![explanatory), visit http://www.gorillatoolkit.org/
Let's dive-in and take a look at how to create a route that's flexible and
uses a regular expression to pass a parameter to our handler:
package main
import (
"github.com/gorilla/mux"
"net/http"
)
const (
PORT = ":8080"
)
This should look familiar to our last code with the exception of the Gorilla
package import:
func pageHandler(w http.ResponseWriter, r
*http.Request) {
vars := mux.Vars(r)
pageID := vars["id"]
fileName := "files/" + pageID + ".html"
http.ServeFile(w,r,fileName)
}
Here, we've created a route handler to accept the response. The thing to
be noted here is the use of mux.Vars, which is a method that will look for
query string variables from the http.Request and parse them into a map.
The values will then be accessible by referencing the result by key, in this
case id, which we'll cover in the next section.
func main() {
rtr := mux.NewRouter()
rtr.HandleFunc("pages{id:[0-9]+}",pageHandler)
http.Handle("/",rtr)
http.ListenAndServe(PORT,nil)
}](https://image.slidesharecdn.com/25097793-250522103318-fa8d3015/85/Go-Building-Web-Applications-1st-Edition-Nathan-Kozyra-Mat-Ryer-52-320.jpg)
![Here, we can see a (very basic) regular expression in the handler. We're
assigning any number of digits after pages to a parameter named id in
{id:[0-9]+}; this is the value we pluck out in pageHandler.
A simpler version that shows how this can be used to delineate separate
pages can be seen by adding a couple of dummy endpoints:
func main() {
rtr := mux.NewRouter()
rtr.HandleFunc("pages{id:[0-9]+}", pageHandler)
rtr.HandleFunc("homepage", pageHandler)
rtr.HandleFunc("contact", pageHandler)
http.Handle("/", rtr)
http.ListenAndServe(PORT, nil)
}
When we visit a URL that matches this pattern, our pageHandler attempts
to find the page in the files/ subdirectory and returns that file directly.
A response to pages1 would look like this:
At this point, you might already be asking, but what if we don't have the
requested page? Or, what happens if we've moved that location? This
brings us to two important mechanisms in web serving—returning error
responses and, as part of that, potentially redirecting requests that have
moved or have other interesting properties that need to be reported back](https://image.slidesharecdn.com/25097793-250522103318-fa8d3015/85/Go-Building-Web-Applications-1st-Edition-Nathan-Kozyra-Mat-Ryer-53-320.jpg)
![Illi robur et æs triplex
Circa pectus erat.
To see the convulsions, agonies, and tortures of a poor
fellow-creature, whom they cannot restore nor recompense,
dying to gratify luxury, and tickle callous and rank organs,
must require a rocky heart, and a great degree of cruelty and
ferocity. I cannot find any great difference, on the foot of
natural reason and equity only, between feeding on human
flesh and feeding on brute animal flesh, except custom and
example.
I believe some [more] rational creatures would suffer less
in being fairly butchered than a strong Ox or red Deer; and,
in natural morality and justice, the degrees of pain here make
the essential difference, for as to other differences, they are
relative only, and can be of no influence with an infinitely
perfect Being. Did not use and example weaken this lesson,
and make the difference, reason alone could never do it.”—
Essay on Regimen, &c. 8vo. 1740. Pages 54 and 70.
Noble and courageous words! Courageous as
coming from an eminent member of a profession—
which almost rivals the legal or even the clerical, in
opposition to all change in the established order of
things. In Dr. Cheyne’s days such interested or
bigoted opposition was even stronger than in the
present time. From the period of the final
establishment of his health, about 1728, little is
known of his life excepting through his writings.
Almost all we know is, that he continued some
fifteen years to practise in London and in Bath with](https://image.slidesharecdn.com/25097793-250522103318-fa8d3015/85/Go-Building-Web-Applications-1st-Edition-Nathan-Kozyra-Mat-Ryer-56-320.jpg)
![distinguished reputation and success. He had
married a daughter of Dr. Middleton of Bristol by
whom he had several children. His only son was born
in 1712. Amongst his intimate friends was the
celebrated Dr. Arbuthnot, a Scotchman like himself,
and we find him meeting Sir Hans Sloane and Dr.
Mead at the bedside of his friend and relative Bishop
Burnet. Both Dr. Arbuthnot and Sir Hans Sloane, we
may remark in passing, have given evidence in
favour of the purer living. His own diet he thus
describes in his Author’s Case, written towards the
end of his life:—
“My regimen, at present, is milk, with tea, coffee, bread
and butter, mild cheese, salads, fruits and seeds of all kinds,
with tender roots (as potatoes, turnips, carrots), and, in
short, everything that has not life, dressed or not, as I like it,
in which there is as much or a greater variety than in animal
foods, so that the stomach need never be cloyed. I drink no
wine nor any fermented liquors, and am rarely dry, most of
my food being liquid, moist, or juicy.[141] Only after dinner I
drink either coffee or green tea, but seldom both in the same
day, and sometimes a glass of soft, small cider. The thinner
my diet, the easier, more cheerful and lightsome I find
myself; my sleep is also the sounder, though perhaps
somewhat shorter than formerly under my full animal diet;
but then I am more alive than ever I was. As soon as I wake I
get up. I rise commonly at six, and go to bed at ten.”
As for the effect of this regimen, he tells us that
“since that time [his last lapse] I thank God I have](https://image.slidesharecdn.com/25097793-250522103318-fa8d3015/85/Go-Building-Web-Applications-1st-Edition-Nathan-Kozyra-Mat-Ryer-57-320.jpg)
![gone on in one constant tenor of diet, and enjoy as
good health as, at my time of life (being now sixty), I
or any man can reasonably expect.” When we
remember the complicity of maladies of which he
had been the victim during his adhesion to the
orthodox mode of living, such experience is
sufficiently significant. Some ten years later he
records his experiences as follows:—
“It is now about sixteen years since, for the last time, I
entered upon a milk and vegetable diet. At the beginning of
this period, this light food I took as my appetite directed,
without any measures, and found myself easy under it. After
some time, I found it became necessary to lessen this
quantity, and I have latterly reduced it to one-half, at most, of
what I at first seemed to bear; and if it should please God to
spare me a few years longer, in order to preserve, in that
case, that freedom and clearness which by his presence I
now enjoy, I shall probably find myself obliged to deny myself
one-half of my present daily sustenance, which, precisely, is
three Winchester pints of new milk, and six ounces of biscuit,
made without salt or yeast, baked in a quick oven.”[142]—
[Natural Method of Curing Diseases, &c., page 298; see also
Preface to Essay on Regimen].
The last production of Dr. Cheyne was his
“Natural Method of Curing the Diseases of the Body,
and the Disorders of the Mind Depending on the
Body. In three parts. Part I.—General Reflections on
the Economy of Nature in Animal Life. Part II.—The
Means and Methods for Preserving Life and Faculties;](https://image.slidesharecdn.com/25097793-250522103318-fa8d3015/85/Go-Building-Web-Applications-1st-Edition-Nathan-Kozyra-Mat-Ryer-58-320.jpg)
![[its principles], in particular cases and diseases,
confirmed by forty years’ experience and
observation.” It is the most practical of all his works,
and is full of valuable observations. Very just and
useful is his rebuke of that sort of John-Bullism which
affects to hold “good living” not only as harmless but
even as a sort of merit—
“How it may be in other countries and religions I will not
say, but among us good Protestants, abstinence, temperance,
and moderation (at least in eating), are so far from being
thought a virtue, and their contrary a vice, that it would seem
that not eating the fattest and most delicious, and to the top,
were the only vice and disease known among us—against
which our parents, relatives, friends, and physicians exclaim
with great vehemence and zeal. And yet, if we consider the
matter attentively we shall find there is no such danger in
abstinence as we imagine, but, on the contrary, the greatest
abstinence and moderation nature and its external laws will
suffer us to go into and practise for any time, will neither
endanger our health, nor weaken our just thinking, be it ever
so unlimited or unrestrained.... And it is a wise providence
that Lent time falls out at that season which, if kept according
to its original intention, in seeds and vegetables well dressed
and not in rich high-dressed fish, would go a great way to
preserve the health of the people in general, as well as
dispose them to seriousness and reflection—so true it is that
‘godliness has the promise of this life, and of that which is to
come,’ and it is very observable that in all civil and established
religious worships hitherto known among polished nations
Lents, days of abstinence, seasons of fasting and bringing
down the brutal part of the rational being, have had a large
share, and been reckoned an indispensable part of their](https://image.slidesharecdn.com/25097793-250522103318-fa8d3015/85/Go-Building-Web-Applications-1st-Edition-Nathan-Kozyra-Mat-Ryer-60-320.jpg)
![undertaking he is one of the few medical writers who
have been completely successful. His productions,
which were much read and had an extensive
influence in their day, procured him a considerable
degree of reputation, not only with the public, but
also with the members of his own profession. If they
present to the reader no great discoveries (?) they
possess the merit of putting more prominently
forward some useful but neglected truths; and
though now, probably, but little read, they contain
much matter that is well worth studying, and have
obtained for their author a respectable place in the
history of medical literature.”[143]
Our notice of the author of the Essay on
Regimen, &c., would scarcely be complete without
some reference to his friendship with two
distinguished characters—John Wesley and Samuel
Richardson,[144]
the author of Pamela. It was to Dr.
Cheyne that Wesley, as he tells us in his journals,
was indebted for his conversion to those dietetic
principles to which he attributes, in great measure,
the invigoration of his naturally feeble constitution,
and which enabled him to undergo an amount of
fatigue and toil, both mentally and bodily, seldom or
never surpassed. Of Cheyne’s friendship for
Richardson there are several memorials preserved in
his familiar letters to that popular writer; and his free](https://image.slidesharecdn.com/25097793-250522103318-fa8d3015/85/Go-Building-Web-Applications-1st-Edition-Nathan-Kozyra-Mat-Ryer-64-320.jpg)
![and in particular the Essay on Man (1732–1735), the
most important of his productions—that we are
especially concerned.
As is pretty well known, these Essays owe their
conception, in great part, to his intimate friend St.
John Bolingbroke. Although the author by birth and,
perhaps, still more from a feeling of pride which
might make him reluctant to abandon an
unfashionable sect (such it was at that time),
belonged nominally to the Old Church, the theology
and metaphysics of the work display little of
ecclesiastical orthodoxy. The pervading principles of
the Essay on Man are natural theology or, as
Warburton styles it, “Naturalism” (i.e., the putting
aside human assertion for the study of the attributes
of Deity through its visible manifestations) and
Optimism.[145]
The merits of the Essay, it must be added, consist
not so much in the philosophy of the poem as a
whole as in the many fine and true thoughts
scattered throughout it, which the author’s
epigrammatic terseness indelibly fixes in the mind. Of
the whole poem the most valuable part, undoubtedly,
is its ridicule of the common arrogant (pretended)
belief that all other species on the earth have been
brought into being for the benefit of the human race
—an egregious fallacy, by the way, which, ably](https://image.slidesharecdn.com/25097793-250522103318-fa8d3015/85/Go-Building-Web-Applications-1st-Edition-Nathan-Kozyra-Mat-Ryer-69-320.jpg)
![“She [Superstition] from the rending earth and bursting skies
Saw gods descend, and fiends infernal rise:
Here fixed the dreadful, there the blest, abodes—
Fear made her devils and weak Hope her gods—
Gods partial, changeful, passionate, unjust,
Whose attributes were rage, revenge, or lust—
Such as the souls of cowards might conceive,
And, formed like tyrants, tyrants would believe.
* * * * * * * *
Altars grew marble then, and reeked with gore;
Then first the Flamen tasted living food,
Next his grim idol smeared with human blood.
With Heaven’s own thunders shook the earth below,
And played the God an engine on his foe.”
Whenever occasion arises, Pope fails not to
stigmatise the barbarity of slaughtering for food; and
the sæva indignatio urges him to upbraid his fellows
with the slaughter of—
“The lamb thy riot dooms to bleed,
* * * * * * *
Who licks the hand just raised to shed his blood.”
And, again, he expresses his detestation of the
selfishness of our species who—
“Destroy all creatures for their sport or gust.”](https://image.slidesharecdn.com/25097793-250522103318-fa8d3015/85/Go-Building-Web-Applications-1st-Edition-Nathan-Kozyra-Mat-Ryer-72-320.jpg)
![That all this was no mere affectation of feeling
appears from his correspondence and contributions
to the periodicals of the time:—
“I cannot think it extravagant,” he writes, “to imagine that
mankind are no less, in proportion, accountable for the ill use
of their dominion over the lower ranks of beings, than for the
exercise of tyranny over their own species. The more entirely
the inferior creation is submitted to our power, the more
answerable we must be for our mismanagement of them; and
the rather, as the very condition of Nature renders them
incapable of receiving any recompense in another life for ill-
treatment in this.”[146]
Consistently with the expression of this true
philosophy, he declares elsewhere that—
“Nothing can be more shocking and horrid than one of our
kitchens sprinkled with blood, and abounding with the cries of
expiring victims, or with the limbs of dead animals scattered
or hung up here and there. It gives one the image of a giant’s
den in romance, bestrewed with scattered heads and
mangled limbs.”[147]
The personal character of Pope, we may add, has
of late been subjected to minute and searching
criticism. Some meannesses, springing from an
extreme anxiety for fame with after ages, have
undoubtedly tarnished his reputation for candour. His
excessive animosity towards his public or private
enemies may be palliated in part, if not excused, by](https://image.slidesharecdn.com/25097793-250522103318-fa8d3015/85/Go-Building-Web-Applications-1st-Edition-Nathan-Kozyra-Mat-Ryer-73-320.jpg)
![the Houyhnhnms—amongst other things, launched
against the indiscriminating diet of his countrymen:—
“I told him” [the Master-Horse], says Gulliver, “we fed on a
thousand things which operated contrary to each other—that
we eat when we are not hungry, and drink without the
provocation of thirst ... that it would be endless to give him a
catalogue of all diseases incident to human bodies, for they
could not be fewer than five or six hundred, spread over
every limb and joint—in short, every part, external and
intestine, having diseases appropriated to itself—to remedy
which there was a sort of people bred up among us in the
profession or pretence of curing the sick.”
Among the infinite variety of remedies and
prescriptions, in the human Materia Medica, the
astounded Houyhnhnm learns, are reckoned
“serpents, toads, frogs, spiders, dead men’s flesh
and bones, birds, beasts, fishes”—no mere travellers’
tales (it is perhaps necessary to explain), but sober
fact, as any one may discover for himself by an
examination of some of the received and popular
medical treatises of the seventeenth century, in
which the most absurd “prescriptions,” involving the
most frightful cruelty, are recorded with all
seriousness:—
“My master, continuing his discourse, said there was
nothing that rendered the Yahoos more odious than their
undistinguishing appetite to devour everything that came in
their way, whether herbs, roots, berries, the corrupted flesh](https://image.slidesharecdn.com/25097793-250522103318-fa8d3015/85/Go-Building-Web-Applications-1st-Edition-Nathan-Kozyra-Mat-Ryer-75-320.jpg)
![of animals, or all mingled together; and that it was peculiar in
their temper that they were fonder of what they could get by
rapine or stealth at a greater distance than much better food
provided for them at home. If their prey held out, they would
eat till they were ready to burst.”
Although unaccustomed to the better living, and
finding it “insipid at first,” the human slave of the
Houyhnhnm (a word which, by the way, in that
language, means “the perfection of nature”) records
as the result of his experience, in the first place, how
little will sustain human life; and, in the second
place, the fact of the superior healthfulness of the
vegetable food.[148]
About this period or a little earlier, Philippe
Hecquet, a French physician, published his Traité des
Dispenses du Carême (“Treatise on Dispensations in
Lent”), 1709, in which he gave in his adhesion to the
principles of Vegetarianism—at all events, so far as
health is concerned. He is mentioned by Voltaire, and
is supposed to be the original of the doctor Sangrado
of Le Sage.[149]
If this conjecture have any truth, the
author of Gil Blas is open to the grave charge of
misrepresentation, of sacrificing truth to effect, or
(what is still worse and still more common) of
pandering to popular prejudices.[150]](https://image.slidesharecdn.com/25097793-250522103318-fa8d3015/85/Go-Building-Web-Applications-1st-Edition-Nathan-Kozyra-Mat-Ryer-76-320.jpg)
![“And yet the wholesome herb neglected dies,
Though with the pure exhilarating soul
Of nutriment and health, and vital powers
Beyond the search of Art, ’tis copious blessed.
For, with hot ravin fired, ensanguined Man
Is now become the Lion of the plain
And worse. The Wolf, who from the nightly fold
Fierce drags the bleating Prey, ne’er drank her milk,
Nor wore her warming fleece; nor has the Steer,
At whose strong chest the deadly Tiger hangs,
E’er ploughed for him. They, too, are tempered high,
With hunger stung and wild necessity,
Nor lodges pity in their shaggy breast.
But Man, whom Nature formed of milder clay,
With every kind emotion in his heart,
And taught alone to weep; while from her lap
She pours ten thousand delicacies—herbs
And fruits, as numerous as the drops of rain
Or beams that gave them birth—shall he, fair form,
Who wears sweet smiles and looks erect on heaven,
E’er stoop to mingle with the prowling herd
And dip his tongue in gore? The beast of prey,
Blood-stained, deserves to bleed. But you, ye Flocks,
What have you done? Ye peaceful people, what
To merit death? You who have given us milk
In luscious streams, and lent us your own coat
Against the winter’s cold? And the plain Ox,
That harmless, honest, guileless animal,
In what has he offended? He, whose toil,
Patient and ever ready, clothes the land
With all the pomp of harvest—shall he bleed,
And struggling groan beneath the cruel hands
E’en of the clowns he feeds, and that, perhaps,
To swell the riot of the autumnal feast
W b hi l b ?”[151]](https://image.slidesharecdn.com/25097793-250522103318-fa8d3015/85/Go-Building-Web-Applications-1st-Edition-Nathan-Kozyra-Mat-Ryer-81-320.jpg)
![Won by his labour?”[151]
And again in denouncing the amateur
slaughtering (euphemised by the mocking term of
Sport) unblushingly perpetrated in the broad light of
day:—
“When beasts of prey retire, that all night long,
Urged by necessity, had ranged the dark,
As if their conscious ravage shunned the light,
Ashamed. Not so [he reproaches] the steady tyrant Man,
Who with the thoughtless insolence of Power,
Inflamed beyond the most infuriate wrath
Of the worst monster that e’er roamed the waste,
For Sport alone pursues the cruel chase,
Amid the beamings of the gentle days.
Upbraid, ye ravening tribes, our wanton rage,
For hunger kindles you, and lawless want;
But lavish fed, in Nature’s bounty rolled—
To joy at anguish, and delight in blood—
Is what your horrid bosoms never knew.”[152]
We conclude these extracts from The Seasons
with the poet’s indignant reflection upon the selfish
greed of Commerce, which barbarously sacrifices by
thousands (as it does also the innocent mammalia of
the seas) the noblest and most sagacious of the
terrestrial races for the sake of a superfluous luxury:
—](https://image.slidesharecdn.com/25097793-250522103318-fa8d3015/85/Go-Building-Web-Applications-1st-Edition-Nathan-Kozyra-Mat-Ryer-82-320.jpg)
![“Peaceful, beneath primeval trees, that cast
Their ample shade o’er Niger’s yellow stream,
And where the Ganges rolls his sacred waves;
Or mid the central depth of blackening woods,
High raised in solemn theatre around,
Leans the huge Elephant, wisest of brutes!
O truly wise! with gentle might endowed:
Though powerful, not destructive. Here he sees
Revolving ages sweep the changeful Earth,
And empires rise and fall: regardless he
Of what the never-resting race of men
Project. Thrice happy! could he ’scape their guile
Who mine, from cruel avarice, his steps:
Or with his towering grandeur swell their state—
The pride of kings!—or else his strength pervert,
And bid him rage amid the mortal fray,
Astonished at the madness of mankind.”[153]](https://image.slidesharecdn.com/25097793-250522103318-fa8d3015/85/Go-Building-Web-Applications-1st-Edition-Nathan-Kozyra-Mat-Ryer-83-320.jpg)
Go Building Web Applications 1st Edition Nathan Kozyra Mat Ryer
- 1. Go Building Web Applications 1st Edition Nathan Kozyra Mat Ryer download https://ebookbell.com/product/go-building-web-applications-1st- edition-nathan-kozyra-mat-ryer-50195586 Explore and download more ebooks at ebookbell.com
- 2. Here are some recommended products that we believe you will be interested in. You can click the link to download. Go Building Web Applications Kozyra Nathanmat Ryer https://ebookbell.com/product/go-building-web-applications-kozyra- nathanmat-ryer-11860662 Cloud Native Go Building Web Applications And Microservices For The Cloud With Go And React 1st Edition Dan Nemeth https://ebookbell.com/product/cloud-native-go-building-web- applications-and-microservices-for-the-cloud-with-go-and-react-1st- edition-dan-nemeth-5655212 Cloud Native Go Building Web Applications And Microservices For The Cloud With Go And React Dan Nemeth https://ebookbell.com/product/cloud-native-go-building-web- applications-and-microservices-for-the-cloud-with-go-and-react-dan- nemeth-5709616 Web Programming With Go Building And Scaling Interactive Web Applications With Gos Robust Ecosystem Ian Taylor https://ebookbell.com/product/web-programming-with-go-building-and- scaling-interactive-web-applications-with-gos-robust-ecosystem-ian- taylor-54303326
- 3. Lets Go Further Advanced Patterns For Building Apis And Web Applications In Go 110 Alex Edwards https://ebookbell.com/product/lets-go-further-advanced-patterns-for- building-apis-and-web-applications-in-go-110-alex-edwards-38438846 Building Distributed Applications In Gin A Handson Guide For Go Developers To Build And Deploy Distributed Web Apps With The Gin Framework Mohamed Labouardy https://ebookbell.com/product/building-distributed-applications-in- gin-a-handson-guide-for-go-developers-to-build-and-deploy-distributed- web-apps-with-the-gin-framework-mohamed-labouardy-35015480 Web Development With Go Building Scalable Web Apps And Restful Services 1st Ed 2015 Shiju Varghese https://ebookbell.com/product/web-development-with-go-building- scalable-web-apps-and-restful-services-1st-ed-2015-shiju- varghese-5299546 Building Restful Web Services With Go Learn How To Build Powerful Restful Apis With Golang That Scale Gracefully 1st Edition Naren Yellavula https://ebookbell.com/product/building-restful-web-services-with-go- learn-how-to-build-powerful-restful-apis-with-golang-that-scale- gracefully-1st-edition-naren-yellavula-52767254 Building Restful Web Services With Go Naren Yellavula https://ebookbell.com/product/building-restful-web-services-with-go- naren-yellavula-230435390
- 6. Table of Contents Go: Building Web Applications Go: Building Web Applications Credits Preface What this learning path covers What you need for this learning path Who this learning path is for Reader feedback Customer support Downloading the example code Errata Piracy Questions 1. Module 1 1. Introducing and Setting Up Go Installing Go Structuring a project Code conventions Importing packages Handling private repositories Dealing with versioning Introducing the net package Hello, Web Summary 2. Serving and Routing Serving files directly Basic routing Using more complex routing with Gorilla Redirecting requests Serving basic errors Summary 3. Connecting to Data Connecting to a database
- 7. Creating a MySQL database Using GUID for prettier URLs Handling 404s Summary 4. Using Templates Introducing templates, context, and visibility HTML templates and text templates Displaying variables and security Using logic and control structures Summary 5. Frontend Integration with RESTful APIs Setting up the basic API endpoint RESTful architecture and best practices Creating our first API endpoint Implementing security Creating data with POST Modifying data with PUT Summary 6. Sessions and Cookies Setting cookies Capturing user information Creating users Enabling sessions Letting users register Letting users log in Initiating a server-side session Creating a store Utilizing flash messages Summary 7. Microservices and Communication Introducing the microservice approach Pros and cons of utilizing microservices Understanding the heart of microservices Communicating between microservices Putting a message on the wire Reading from another service Summary
- 8. 8. Logging and Testing Introducing logging in Go Logging to IO Multiple loggers Formatting your output Using panics and fatal errors Introducing testing in Go Summary 9. Security HTTPS everywhere – implementing TLS Preventing SQL injection Protecting against XSS Preventing cross-site request forgery (CSRF) Securing cookies Using the secure middleware Summary 10. Caching, Proxies and Improved Performance Identifying bottlenecks Implementing reverse proxies Implementing caching strategies Using Least Recently Used Caching by file Caching in memory Implementing HTTP/2 Summary 2. Module 2 1. Chat Application with Web Sockets A simple web server Templates Doing things once Using your own handlers Properly building and executing Go programs Modeling a chat room and clients on the server Modeling the client Modeling a room Concurrency programming using idiomatic Go Turning a room into an HTTP handler
- 9. Use helper functions to remove complexity Creating and using rooms Building an HTML and JavaScript chat client Getting more out of templates Tracing code to get a look under the hood Writing a package using TDD Interfaces Unit tests Red-green testing Implementing the interface Unexported types being returned to users Using our new trace package Making tracing optional Clean package APIs Summary 2. Adding Authentication Handlers all the way down Making a pretty social sign-in page Endpoints with dynamic paths OAuth2 Open source OAuth2 packages Tell the authentication providers about your app Implementing external logging in Logging in Handling the response from the provider Presenting the user data Augmenting messages with additional data Summary 3. Three Ways to Implement Profile Pictures Avatars from the authentication server Getting the avatar URL Transmitting the avatar URL Adding the avatar to the user interface Logging out Making things prettier Implementing Gravatar Abstracting the avatar URL process
- 10. The authentication service and avatar's implementation Using an implementation Gravatar implementation Uploading an avatar picture User identification An upload form Handling the upload Serving the images The Avatar implementation for local files Supporting different file types Refactoring and optimizing our code Replacing concrete types with interfaces Changing interfaces in a test-driven way Fixing existing implementations Global variables versus fields Implementing our new design Tidying up and testing Combining all three implementations Summary 4. Command-line Tools to Find Domain Names Pipe design for command-line tools Five simple programs Sprinkle Exercise – configurable transformations Domainify Exercise – making top-level domains configurable Coolify Synonyms Using environment variables for configuration Consuming a web API Getting domain suggestions Available Composing all five programs One program to rule them all Summary 5. Building Distributed Systems and Working with Flexible Data System design
- 11. Database design Installing the environment NSQ NSQ driver for Go MongoDB MongoDB driver for Go Starting the environment Votes from Twitter Authorization with Twitter Extracting the connection Reading environment variables Reading from MongoDB Reading from Twitter Signal channels Publishing to NSQ Gracefully starting and stopping Testing Counting votes Connecting to the database Consuming messages in NSQ Keeping the database updated Responding to Ctrl + C Running our solution Summary 6. Exposing Data and Functionality through a RESTful Data Web Service API RESTful API design Sharing data between handlers Wrapping handler functions API key Database session Per request variables Cross-browser resource sharing Responding Understanding the request A simple main function to serve our API Using handler function wrappers
- 12. Handling endpoints Using tags to add metadata to structs Many operations with a single handler Reading polls Creating a poll Deleting a poll CORS support Testing our API using curl A web client that consumes the API An index page showing a list of polls A page to create a new poll A page to show details of the poll Running the solution Summary 7. Random Recommendations Web Service Project overview Project design specifics Representing data in code Public views of Go structs Generating random recommendations Google Places API key Enumerators in Go Test-driven enumerator Querying the Google Places API Building recommendations Handlers that use query parameters CORS Testing our API Web application Summary 8. Filesystem Backup Solution design Project structure Backup package Obvious interfaces? Implementing ZIP Has the filesystem changed?
- 13. Checking for changes and initiating a backup Hardcoding is OK for a short while The user command-line tool Persisting small data Parsing arguments Listing the paths String representations for your own types Adding paths Removing paths Using our new tool The daemon backup tool Duplicated structures Caching data Infinite loops Updating filedb records Testing our solution Summary 3. Module 3 1. An Introduction to Concurrency in Go Introducing goroutines A patient goroutine Implementing the defer control mechanism Using Go's scheduler Using system variables Understanding goroutines versus coroutines Implementing channels Channel-based sorting at the letter capitalization factory Cleaning up our goroutines Buffered or unbuffered channels Using the select statement Closures and goroutines Building a web spider using goroutines and channels Summary 2. Understanding the Concurrency Model Understanding the working of goroutines Synchronous versus asynchronous goroutines Designing the web server plan
- 14. Visualizing concurrency RSS in action An RSS reader with self diagnostics Imposing a timeout A little bit about CSP The dining philosophers problem Go and the actor model Object orientation Demonstrating simple polymorphism in Go Using concurrency Managing threads Using sync and mutexes to lock data Summary 3. Developing a Concurrent Strategy Applying efficiency in complex concurrency Identifying race conditions with race detection Using mutual exclusions Exploring timeouts Importance of consistency Synchronizing our concurrent operations The project – multiuser appointment calendar Visualizing a concurrent pattern Developing our server requirements Web server The Gorilla toolkit Using templates Time Endpoints Custom structs A multiuser Appointments Calendar A note on style A note on immutability Summary 4. Data Integrity in an Application Getting deeper with mutexes and sync The cost of goroutines Working with files
- 15. Getting low – implementing C Touching memory in cgo The structure of cgo The other way around Getting even lower – assembly in Go Distributed Go Some common consistency models Distributed shared memory First-in-first-out – PRAM Looking at the master-slave model The producer-consumer problem Looking at the leader-follower model Atomic consistency / mutual exclusion Release consistency Using memcached Circuit Summary 5. Locks, Blocks, and Better Channels Understanding blocking methods in Go Blocking method 1 – a listening, waiting channel Sending more data types via channels Creating a function channel Using an interface channel Using structs, interfaces, and more complex channels The net package – a chat server with interfaced channels Handling direct messages Examining our client Blocking method 2 – the select statement in a loop Cleaning up goroutines Blocking method 3 – network connections and reads Creating channels of channels Pprof – yet another awesome tool Handling deadlocks and errors Summary 6. C10K – A Non-blocking Web Server in Go Attacking the C10K problem Failing of servers at 10,000 concurrent connections
- 16. Using concurrency to attack C10K Taking another approach Building our C10K web server Benchmarking against a blocking web server Handling requests Routing requests Serving pages Parsing our template External dependencies Connecting to MySQL Multithreading and leveraging multiple cores Exploring our web server Timing out and moving on Summary 7. Performance and Scalability High performance in Go Getting deeper into pprof Parallelism's and concurrency's impact on I/O pprof Using the App Engine Distributed Go Types of topologies Type 1 – star Type 2 – mesh The Publish and Subscribe model Serialized data Remote code execution Other topologies Message Passing Interface Some helpful libraries Nitro profiler Heka GoFlow Memory preservation Garbage collection in Go Summary 8. Concurrent Application Architecture Designing our concurrent application
- 17. Identifying our requirements Using NoSQL as a data store in Go MongoDB Redis Tiedot CouchDB Cassandra Couchbase Setting up our data store Monitoring filesystem changes Managing logfiles Handling configuration files Detecting file changes Sending changes to clients Checking records against Couchbase Backing up our files Designing our web interface Reverting a file's history – command line Using Go in daemons and as a service Checking the health of our server Summary 9. Logging and Testing Concurrency in Go Handling errors and logging Breaking out goroutine logs Using the LiteIDE for richer and easier debugging Sending errors to screen Logging errors to file Logging errors to memory Using the log4go package for robust logging Panicking Recovering Logging our panics Catching stack traces with concurrent code Using the runtime package for granular stack traces Summary 10. Advanced Concurrency and Best Practices Going beyond the basics with channels
- 18. Building workers Implementing nil channel blocks Using nil channels Implementing more granular control over goroutines with tomb Timing out with channels Building a load balancer with concurrent patterns Choosing unidirectional and bidirectional channels Using receive-only or send-only channels Using an indeterminate channel type Using Go with unit testing GoCheck Ginkgo and Gomega Using Google App Engine Utilizing best practices Structuring your code Documenting your code Making your code available via go get Keeping concurrency out of your packages Summary A. Bibliography Index
- 19. Go: Building Web Applications
- 20. Go: Building Web Applications Build real-world, production-ready solutions by harnessing the powerful features of Go A course in three modules BIRMINGHAM - MUMBAI
- 21. Go: Building Web Applications Copyright © 2016 Packt Publishing All rights reserved. No part of this course may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews. Every effort has been made in the preparation of this course to ensure the accuracy of the information presented. However, the information contained in this course is sold without warranty, either express or implied. Neither the authors, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this course. Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this course by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information. Published on: August 2016 Published by Packt Publishing Ltd. Livery Place 35 Livery Street Birmingham B3 2PB, UK. ISBN 978-1-78712-349-6 www.packtpub.com
- 22. Credits Authors Nathan Kozyra Mat Ryer Reviewers Karthik Nayak Tyler Bunnell Michael Hamrah Nimish Parmar Jeremy R. Budnack János Fehér Aleksandar S. Sokolovski Michele Della Torre Content Development Editor Arun Nadar Graphics Abhinash Sahu Production Coordinator Melwyn D'sa
- 23. Preface Since the late 1980s and early 1990s, there has been a slow flood of powerful new languages and paradigms—Perl, Python, Ruby, PHP, and JavaScript—have taken an expanding user base by storm and has become one of the most popular languages (up there with stalwarts such as C, C++, and Java). Multithreading, memory caching, and APIs have allowed multiple processes, dissonant languages, applications, and even separate operating systems to work in congress. And while this is great, there's a niche that until very recently was largely unserved: powerful, compiled, cross-platform languages with concurrency support that are geared towards systems programmers. So when Google announced Go in 2009, which included some of the best minds in language design (and programming in general)—Rob Pike and Ken Thompson of Bell Labs fame and Robert Griesemer, who worked on Google's JavaScript implementation V8—to design a modern, concurrent language with development ease at the forefront. For Go programming bright future, the team focused on some sore spots in the alternatives, which are as follows: Dynamically typed languages have—in recent years—become incredibly popular. Go eschews the explicit, "cumbersome" type systems of Java or C++. Go uses type inference, which saves development time, but is still also strongly typed. Concurrency, parallelism, pointers/memory access, and garbage collection are unwieldy in the aforementioned languages. Go lets these concepts be as easy or as complicated as you want or need them to be. As a newer language, Go has a focus on multicore design that was a necessary afterthought in languages such as C++. Go's compiler is super-fast; it's so fast that there are implementations of it that treat Go code as interpreted. Although Google designed Go to be a systems language, it's versatile enough to be used in a myriad of ways. Certainly, the focus
- 24. on advanced, cheap concurrency makes it ideal for network and systems programming. Go is loose with syntax, but strict with usage. By this we mean that Go will let you get a little lazy with some lexer tokens, but you still have to produce fundamentally tight code. As Go provides a formatting tool that attempts to clarify your code, you can also spend less time on readability concerns as you're coding What this learning path covers Module 1, Learning Go Web Development, starts off with introducing and setting up Go before you move on to produce responsive servers that react to certain web endpoint. You will then implement database connections to acquire data and then present it to our users using different template packages. Later on, you will learn about sessions and cookies to retain information before delving with the basics of microservices. By the end of this module, we will be covering the testing, debugging, and the security aspect. Module 2, Go Programming Blueprints, has a project-based approach where you will be building chat application, adding authentication, and adding your own profile pictures in different ways. You will learn how Go makes it easy to build powerful command-line tools to find domain names before building a highly scalable Twitter polling and vote counting engine powered by NSQ and MongoDB. Later on it covers the functionalities of RESTful Data Web Service API and Google Places API before you move on to build a simple but powerful filesystem backup tool for our code projects. Module 3, Mastering Concurrency in Go, introduces you to Concurrency in Go where you will be understanding the Concurrency model and developing a strategy for designing applications. You will learn to create basic and complex communication channels between our goroutines to manage data not only across single or multithreaded systems but also distributed systems. Later on you will be tackling a real-world problem, that is, being able to develop a high performance web server that can
- 25. handle a very large volume of live, active traffic. You will then learn how to scale your application and make it capable of being expanded in scope, design, and/or capacity. It will then focus on when and where to implement concurrent patterns, utilize parallelism, and ensure data consistency. At the end of this module, we will be logging and testing concurrency before we finally look at the best practices on how to implement complicated and advanced techniques offered by Go.
- 26. What you need for this learning path For this course, any modern computers running a standard Linux flavor, OS X or Windows should be enough to get started. You can find a full list of requirements at https://golang.org/dl/. Later on, you'll also need to have the following software installed: MySQL (http://dev.mysql.com/downloads/) Couchbase (http://www.couchbase.com/download) Your choice of IDE is a matter of personal preference.
- 27. Who this learning path is for This course is intended for developers who are new to Go but have previous experience of building web applications and APIs. It is also targeted towards systems or network programmer with some knowledge of Go and concurrency, but would like to know about the implementation of concurrent systems written in Go
- 28. Reader feedback Feedback from our readers is always welcome. Let us know what you think about this course—what you liked or disliked. Reader feedback is important for us as it helps us develop titles that you will really get the most out of. To send us general feedback, simply e-mail <feedback@packtpub.com>, and mention the course's title in the subject of your message. If there is a topic that you have expertise in and you are interested in either writing or contributing to a book, see our author guide at www.packtpub.com/authors.
- 29. Customer support Now that you are the proud owner of a Packt course, we have a number of things to help you to get the most from your purchase. Downloading the example code You can download the example code files for this course from your account at http://www.packtpub.com. If you purchased this course elsewhere, you can visit http://www.packtpub.com/support and register to have the files emailed directly to you. You can download the code files by following these steps: 1. Log in or register to our website using your e-mail address and password. 2. Hover the mouse pointer on the SUPPORT tab at the top. 3. Click on Code Downloads & Errata. 4. Enter the name of the course in the Search box. 5. Select the course for which you're looking to download the code files. 6. Choose from the drop-down menu where you purchased this course from. 7. Click on Code Download. You can also download the code files by clicking on the Code Files button on the course's webpage at the Packt Publishing website. This page can be accessed by entering the course's name in the Search box. Please note that you need to be logged in to your Packt account. Once the file is downloaded, please make sure that you unzip or extract the folder using the latest version of: WinRAR / 7-Zip for Windows Zipeg / iZip / UnRarX for Mac 7-Zip / PeaZip for Linux
- 30. The code bundle for the course is also hosted on GitHub at https://github.com/PacktPublishing/repository-name. We also have other code bundles from our rich catalog of books and videos available at https://github.com/PacktPublishing/. Check them out! Errata Although we have taken every care to ensure the accuracy of our content, mistakes do happen. If you find a mistake in one of our courses —maybe a mistake in the text or the code—we would be grateful if you could report this to us. By doing so, you can save other readers from frustration and help us improve subsequent versions of this course. If you find any errata, please report them by visiting http://www.packtpub.com/submit-errata, selecting your course, clicking on the Errata Submission Form link, and entering the details of your errata. Once your errata are verified, your submission will be accepted and the errata will be uploaded to our website or added to any list of existing errata under the Errata section of that title. To view the previously submitted errata, go to https://www.packtpub.com/books/content/support and enter the name of the course in the search field. The required information will appear under the Errata section. Piracy Piracy of copyrighted material on the Internet is an ongoing problem across all media. At Packt, we take the protection of our copyright and licenses very seriously. If you come across any illegal copies of our works in any form on the Internet, please provide us with the location address or website name immediately so that we can pursue a remedy. Please contact us at <copyright@packtpub.com> with a link to the suspected pirated material. We appreciate your help in protecting our authors and our ability to bring you valuable content.
- 31. Questions If you have a problem with any aspect of this course, you can contact us at <questions@packtpub.com>, and we will do our best to address the problem.
- 32. Part 1. Module 1 Learning Go Web Development Build frontend-to-backend web applications using the best practices of a powerful, fast, and easy-to-deploy server language
- 33. Chapter 1. Introducing and Setting Up Go When starting with Go, one of the most common things you'll hear being said is that it's a systems language. Indeed, one of the earlier descriptions of Go, by the Go team itself, was that the language was built to be a modern systems language. It was constructed to combine the speed and power of languages, such as C with the syntactical elegance and thrift of modern interpreted languages, such as Python. You can see that goal realized when you look at just a few snippets of Go code. From the Go FAQ on why Go was created: "Go was born out of frustration with existing languages and environments for systems programming." Perhaps the largest part of present-day Systems programming is designing backend servers. Obviously, the Web comprises a huge, but not exclusive, percentage of that world. Go hasn't been considered a web language until recently. Unsurprisingly, it took a few years of developers dabbling, experimenting, and finally embracing the language to start taking it to new avenues. While Go is web-ready out of the box, it lacks a lot of the critical frameworks and tools people so often take for granted with web development now. As the community around Go grew, the scaffolding began to manifest in a lot of new and exciting ways. Combined with existing ancillary tools, Go is now a wholly viable option for end-to-end web development. But back to that primary question: Why Go? To be fair, it's not right for every web project, but any application that can benefit from high-performance, secure web-serving out of the box with the added benefits of a beautiful concurrency model would make for a good
- 34. benefits of a beautiful concurrency model would make for a good candidate. In this book, we're going to explore those aspects and others to outline what can make Go the right language for your web architecture and applications. We're not going to deal with a lot of the low-level aspects of the Go language. For example, we assume you're familiar with variable and constant declaration. We assume you understand control structures. In this chapter we will cover the following topics: Installing Go Structuring a project Importing packages Introducing the net package Hello, Web Installing Go The most critical first step is, of course, making sure that Go is available and ready to start our first web server. Note While one of Go's biggest selling points is its cross-platform support (both building and using locally while targeting other operating systems), your life will be much easier on a Nix compatible platform. If you're on Windows, don't fear. Natively, you may run into incompatible packages, firewall issues when running using go run command and some other quirks, but 95% of the Go ecosystem will be available to you. You can also, very easily, run a virtual machine, and in fact that is a great way to simulate a potential production environment.
- 35. In-depth installation instructions are available at https://golang.org/doc/install, but we'll talk about a few quirky points here before moving on. For OS X and Windows, Go is provided as a part of a binary installation package. For any Linux platform with a package manager, things can be pretty easy. Note To install via common Linux package managers: Ubuntu: sudo apt-get golang CentOS: sudo yum install golang On both OS X and Linux, you'll need to add a couple of lines to your path —the GOPATH and PATH. First, you'll want to find the location of your Go binary's installation. This varies from distribution to distribution. Once you've found that, you can configure the PATH and GOPATH, as follows: export PATH=$PATH:usrlocal/go/bin export GOPATH="usrshare/go" While the path to be used is not defined rigidly, some convention has coalesced around starting at a subdirectory directly under your user's home directory, such as $HOME/go or ~Home/go. As long as this location is set perpetually and doesn't change, you won't run into issues with conflicts or missing packages. You can test the impact of these changes by running the go env command. If you see any issues with this, it means that your directories are not correct. Note that this may not prevent Go from running—depending on whether the GOBIN directory is properly set—but will prevent you from installing packages globally across your system.
- 36. To test the installation, you can grab any Go package by a go get command and create a Go file somewhere. As a quick example, first get a package at random, we'll use a package from the Gorilla framework, as we'll use this quite a bit throughout this book. go get github.com/gorilla/mux If this runs without any issue, Go is finding your GOPATH correctly. To make sure that Go is able to access your downloaded packages, draw up a very quick package that will attempt to utilize Gorilla's mux package and run it to verify whether the packages are found. package main import ( "fmt" "github.com/gorilla/mux" "net/http" ) func TestHandler(w http.ResponseWriter, r *http.Request) { } func main() { router := mux.NewRouter() router.HandleFunc("test", TestHandler) http.Handle("", router) fmt.Println("Everything is set up!") } Run go run test.go in the command line. It won't do much, but it will deliver the good news as shown in the following screenshot:
- 37. Structuring a project When you're first getting started and mostly playing around, there's no real problem with setting your application lazily. For example, to get started as quickly as possible, you can create a simple hello.go file anywhere you like and compile without issue. But when you get into environments that require multiple or distinct packages (more on that shortly) or have more explicit cross-platform requirements, it makes sense to design your project in a way that will facilitate the use of the go build tool. The value of setting up your code in this manner lies in the way that the go build tool works. If you have local (to your project) packages, the build tool will look in the src directory first and then your GOPATH. When you're building for other platforms, go build will utilize the local bin folder to organize the binaries. When building packages that are intended for mass use, you may also find that either starting your application under your GOPATH directory and then symbolically linking it to another directory, or doing the opposite, will allow you to develop without the need to subsequently go get your own code. Code conventions As with any language, being a part of the Go community means perpetual consideration of the way others create their code. Particularly if you're going to work in open source repositories, you'll want to generate your code the way that others do, in order to reduce the amount of friction when people get or include your code. One incredibly helpful piece of tooling that the Go team has included is go fmt. fmt here, of course, means format and that's exactly what this tool does, it automatically formats your code according to the designed
- 38. conventions. By enforcing style conventions, the Go team has helped to mitigate one of the most common and pervasive debates that exist among a lot of other languages. While the language communities tend to drive coding conventions, there are always little idiosyncrasies in the way individuals write programs. Let's use one of the most common examples around—where to put the opening bracket. Some programmers like it on the same line as the statement: for (int i = 0; i < 100; i++) { // do something } While others prefer it on the subsequent line: for (int i = 0; i < 100; i++) { // do something } These types of minor differences spark major, near-religious debates. The Gofmt tool helps alleviate this by allowing you to yield to Go's directive. Now, Go bypasses this obvious source of contention at the compiler, by formatting your code similar to the latter example discussed earlier. The compiler will complain and all you'll get is a fatal error. But the other style choices have some flexibility, which are enforced when you use the tool to format. Here, for example, is a piece of code in Go before go fmt: func Double(n int) int { if (n == 0) {
- 39. return 0 } else { return n * 2 } } Arbitrary whitespace can be the bane of a team's existence when it comes to sharing and reading code, particularly when every team member is not on the same IDE. By running go fmt, we clean this up, thereby translating our whitespace according to Go's conventions: func Double(n int) int { if n == 0 { return 0 } else { return n * 2 } } Long story short: always run go fmt before shipping or pushing your code.
- 40. Importing packages Beyond the absolute and the most trivial application—one that cannot even produce a Hello World output—you must have some imported package in a Go application. To say Hello World, for example, we'd need some sort of a way to generate an output. Unlike in many other languages, even the core language library is accessible by a namespaced package. In Go, namespaces are handled by a repository endpoint URL, which is github.com/nkozyra/gotest, which can be opened directly on GitHub (or any other public location) for the review. Handling private repositories The go get tool easily handles packages hosted at the repositories, such as GitHub, Bitbucket, and Google Code (as well as a few others). You can also host your own projects, ideally a git project, elsewhere, although it might introduce some dependencies and sources for errors, which you'd probably like to avoid. But what about the private repos? While go get is a wonderful tool, you'll find yourself looking at an error without some additional configuration, SSH agent forwarding, and so on. You can work around this in a couple of ways, but one very simple method is to clone the repository locally, using your version control software directly. Dealing with versioning You may have paused when you read about the way namespaces are defined and imported in a Go application. What happens if you're using version 1 of the application but would like to bring in version 2? In most cases, this has to be explicitly defined in the path of the import. For example:
- 41. import ( "github.com/foo/foo-v1" ) versus: import ( "github.com/foo/foo-v2" ) As you might imagine, this can be a particularly sticky aspect of the way Go handles the remote packages. Unlike a lot of other package managers, go get is decentralized—that is, nobody maintains a canonical reference library of packages and versions. This can sometimes be a sore spot for new developers. For the most part, packages are always imported via the go get command, which reads the master branch of the remote repository. This means that maintaining multiple versions of a package at the same endpoint is, for the most part, impossible. It's the utilization of the URL endpoints as namespaces that allows the decentralization, but it's also what provides a lack of internal support for versioning. Your best bet as a developer is to treat every package as the most up-to- date version when you perform a go get command. If you need a newer version, you can always follow whatever pattern the author has decided on, such as the preceding example. As a creator of your own packages, make sure that you also adhere to this philosophy. Keeping your master branch HEAD as the most up-to- date will make sure your that the code fits with the conventions of other Go authors.
- 42. Introducing the net package At the heart of all network communications in Go is the aptly-named net package, which contains subpackages not only for the very relevant HTTP operations, but also for other TCP/UDP servers, DNS, and IP tools. In short, everything you need to create a robust server environment. Of course, what we care about for the purpose of this book lies primarily in the net/http package, but we'll look at a few other functions that utilize the rest of the package, such as a TCP connection, as well as WebSockets. Let's quickly take a look at just performing that Hello World (or Web, in this case) example we have been talking about.
- 43. Hello, Web The following application serves as a static file at the location /static, and a dynamic response at the location /dynamic: package main import ( "fmt" "net/http" "time" ) const ( Port = ":8080" ) func serveDynamic(w http.ResponseWriter, r *http.Request) { response := "The time is now " + time.Now().String() fmt.Fprintln(w,response) } Just as fmt.Println will produce desired content at the console level, Fprintln allows you to direct output to any writer. We'll talk a bit more about the writers in Chapter 2, Serving and Routing, but they represent a fundamental, flexible interface that is utilized in many Go applications, not just for the Web: func serveStatic(w http.ResponseWriter, r *http.Request) { http.ServeFile(w, r, "static.html") } Our serveStatic method just serves one file, but it's trivial to allow it to serve any file directly and use Go as an old-school web server that serves only static content: func main() { http.HandleFunc("static",serveStatic)
- 44. http.HandleFunc("",serveDynamic) http.ListenAndServe(Port,nil) } Feel free to choose the available port of your choice—higher ports will make it easier to bypass the built-in security functionality, particularly in Nix systems. If we take the preceding example and visit the respective URLs—in this case the root at / and a static page at /static, we should see the intended output as shown: At the root, / , the output is as follows: At /static, the output is as follows: As you can see, producing a very simple output for the Web is, well, very simple in Go. The built-in package allows us to create a basic, yet inordinately fast site in Go with just a few lines of code using native packages.
- 45. This may not be very exciting, but before we can run, we must walk. Producing the preceding output introduces a few key concepts. First, we've seen how net/http directs requests using a URI or URL endpoint to helper functions, which must implement the http.ResponseWriter and http.Request methods. If they do not implement it, we get a very clear error on that end. The following is an example that attempts to implement it in this manner: func serveError() { fmt.Println("There's no way I'll work!") } func main() { http.HandleFunc("static", serveStatic) http.HandleFunc("", serveDynamic) http.HandleFunc("/error",serveError) http.ListenAndServe(Port, nil) } The following screenshot shows the resulting error you'll get from Go: You can see that serveError does not include the required parameters and thus results in a compilation error.
- 46. Summary This chapter serves as an introduction to the most basic concepts of Go and producing for the Web in Go, but these points are critical foundational elements for being productive in the language and in the community. We've looked at coding conventions and package design and organization, and we've produced our first program—the all-too-familiar Hello, World application—and accessed it via our localhost. Obviously, we're a long way from a real, mature application for the Web, but the building blocks are essential to getting there. In Chapter 2, Serving and Routing, we'll look at how to direct different requests to different application logic using the built-in routing functionality in Go's net/http package, as well as a couple of third party router packages.
- 47. Chapter 2. Serving and Routing The cornerstone of the Web as a commercial entity—the piece on which marketing and branding has relied on nearly exclusively—is the URL. While we're not yet looking at the top-level domain handling, we need to take up the reins of our URL and its paths (or endpoints). In this chapter, we'll do just this by introducing multiple routes and corresponding handlers. First, we'll do this with a simple flat file serving and then we'll introduce complex mixers to do the routing with more flexibility by implementing a library that utilizes regular expressions in its routes. By the end of this chapter, you should be able to create a site on localhost that can be accessed by any number of paths and return content relative to the requested path. In this chapter, we will cover the following topics: Serving files directly Basic routing Using more complex routing with Gorilla Redirecting requests Serving basic errors Serving files directly In the preceding chapter, we utilized the fmt.Fprintln function to output some generic Hello, World messaging in the browser. This obviously has limited utility. In the earliest days of the Web and web servers, the entirety of the Web was served by directing requests to corresponding static files. In other words, if a user requested home.html, the web server would look for a file called home.html and return it to the user.
- 48. This might seem quaint today, as a vast majority of the Web is now served in some dynamic fashion, with content often being determined via database IDs, which allows for pages to be generated and regenerated without someone modifying the individual files. Let's take a look at the simplest way in which we can serve files in a way similar to those olden days of the Web as shown: package main import ( "net/http" ) const ( PORT = ":8080" ) func main() { http.ListenAndServe(PORT, http.FileServer(http.Dir("varwww"))) } Pretty simple, huh? Any requests made to the site will attempt to find a corresponding file in our local varwww directory. But while this has a more practical use compared to the example in Chapter 1, Introducing and Setting Up Go, it's still pretty limited. Let's take a look at expanding our options a bit.
- 49. Basic routing In Chapter 1, Introducing and Setting Up, we produced a very basic URL endpoint that allowed static file serving. The following are the simple routes we produced for that example: func main() { http.HandleFunc("static",serveStatic) http.HandleFunc("",serveDynamic) http.ListenAndServe(Port,nil) } In review, you can see two endpoints, /static and /, which either serve a single static file or generate output to the http.ResponseWriter. We can have any number of routers sitting side by side. However, consider a scenario where we have a basic website with about, contact, and staff pages, with each residing in varwww/about/index.html, varwww/contact.html, and varwww/staff/home.html. While it's an intentionally obtuse example, it demonstrates the limitations of Go's built- in and unmodified routing system. We cannot route all requests to the same directory locally, we need something that provides more malleable URLs.
- 50. Using more complex routing with Gorilla In the previous session, we looked at basic routing but that can only take us so far, we have to explicitly define our endpoints and then assign them to handlers. What happens if we have a wildcard or a variable in our URL? This is an absolutely essential part of the Web and any serious web server. To invoke a very simple example, consider hosting a blog with unique identifiers for each blog entry. This could be a numeric ID representing a database ID entry or a text-based globally unique identifier, such as my- first-block-entry. Note In the preceding example, we want to route a URL like pages1 to a filename called 1.html. Alternately, in a database-based scenario, we'd want to use pages1 or pageshello-world to map to a database entry with a GUID of 1 or hello-world, respectively. To do this we either need to include an exhaustive list of possible endpoints, which is extremely wasteful, or implement wildcards, ideally through regular expressions. In either case, we'd like to be able to utilize the value from the URL directly within our application. This is simple with URL parameters from GET or POST. We can extract those simply, but they aren't particularly elegant in terms of clean, hierarchical or descriptive URLs that are often necessary for search engine optimization purposes. The built-in net/http routing system is, perhaps by design, relatively simple. To get anything more complicated out of the values in any given request, we either need to extend the routing capabilities or use a package that has done this.
- 51. In the few years that Go has been publicly available and the community has been growing, a number of web frameworks have popped up. We'll talk about these in a little more depth as we continue the book, but one in particular is well-received and very useful: the Gorilla web toolkit. As the name implies, Gorilla is less of a framework and more of a set of very useful tools that are generally bundled in frameworks. Specifically, Gorilla contains: gorilla/context: This is a package for creating a globally-accessible variable from the request. It's useful for sharing a value from the URL without repeating the code to access it across your application. gorilla/rpc: This implements RPC-JSON, which is a system for remote code services and communication without implementing specific protocols. This relies on the JSON format to define the intentions of any request. gorilla/schema: This is a package that allows simple packing of form variables into a struct, which is an otherwise cumbersome process. gorilla/securecookie: This, unsurprisingly, implements authenticated and encrypted cookies for your application. gorilla/sessions: Similar to cookies, this provides unique, long- term, and repeatable data stores by utilizing a file-based and/or cookie-based session system. gorilla/mux: This is intended to create flexible routes that allow regular expressions to dictate available variables for routers. The last package is the one we're most interested in here, and it comes with a related package called gorilla/reverse, which essentially allows you to reverse the process of creating regular expression-based muxes. We will cover that topic in detail in the later section. Note You can grab individual Gorilla packages by their GitHub location with a go get. For example, to get the mux package, going to github.com/gorilla/mux will suffice and bring the package into your GOPATH. For the locations of the other packages (they're fairly self-
- 52. explanatory), visit http://www.gorillatoolkit.org/ Let's dive-in and take a look at how to create a route that's flexible and uses a regular expression to pass a parameter to our handler: package main import ( "github.com/gorilla/mux" "net/http" ) const ( PORT = ":8080" ) This should look familiar to our last code with the exception of the Gorilla package import: func pageHandler(w http.ResponseWriter, r *http.Request) { vars := mux.Vars(r) pageID := vars["id"] fileName := "files/" + pageID + ".html" http.ServeFile(w,r,fileName) } Here, we've created a route handler to accept the response. The thing to be noted here is the use of mux.Vars, which is a method that will look for query string variables from the http.Request and parse them into a map. The values will then be accessible by referencing the result by key, in this case id, which we'll cover in the next section. func main() { rtr := mux.NewRouter() rtr.HandleFunc("pages{id:[0-9]+}",pageHandler) http.Handle("/",rtr) http.ListenAndServe(PORT,nil) }
- 53. Here, we can see a (very basic) regular expression in the handler. We're assigning any number of digits after pages to a parameter named id in {id:[0-9]+}; this is the value we pluck out in pageHandler. A simpler version that shows how this can be used to delineate separate pages can be seen by adding a couple of dummy endpoints: func main() { rtr := mux.NewRouter() rtr.HandleFunc("pages{id:[0-9]+}", pageHandler) rtr.HandleFunc("homepage", pageHandler) rtr.HandleFunc("contact", pageHandler) http.Handle("/", rtr) http.ListenAndServe(PORT, nil) } When we visit a URL that matches this pattern, our pageHandler attempts to find the page in the files/ subdirectory and returns that file directly. A response to pages1 would look like this: At this point, you might already be asking, but what if we don't have the requested page? Or, what happens if we've moved that location? This brings us to two important mechanisms in web serving—returning error responses and, as part of that, potentially redirecting requests that have moved or have other interesting properties that need to be reported back
- 54. to the end users.
- 55. Random documents with unrelated content Scribd suggests to you:
- 56. Illi robur et æs triplex Circa pectus erat. To see the convulsions, agonies, and tortures of a poor fellow-creature, whom they cannot restore nor recompense, dying to gratify luxury, and tickle callous and rank organs, must require a rocky heart, and a great degree of cruelty and ferocity. I cannot find any great difference, on the foot of natural reason and equity only, between feeding on human flesh and feeding on brute animal flesh, except custom and example. I believe some [more] rational creatures would suffer less in being fairly butchered than a strong Ox or red Deer; and, in natural morality and justice, the degrees of pain here make the essential difference, for as to other differences, they are relative only, and can be of no influence with an infinitely perfect Being. Did not use and example weaken this lesson, and make the difference, reason alone could never do it.”— Essay on Regimen, &c. 8vo. 1740. Pages 54 and 70. Noble and courageous words! Courageous as coming from an eminent member of a profession— which almost rivals the legal or even the clerical, in opposition to all change in the established order of things. In Dr. Cheyne’s days such interested or bigoted opposition was even stronger than in the present time. From the period of the final establishment of his health, about 1728, little is known of his life excepting through his writings. Almost all we know is, that he continued some fifteen years to practise in London and in Bath with
- 57. distinguished reputation and success. He had married a daughter of Dr. Middleton of Bristol by whom he had several children. His only son was born in 1712. Amongst his intimate friends was the celebrated Dr. Arbuthnot, a Scotchman like himself, and we find him meeting Sir Hans Sloane and Dr. Mead at the bedside of his friend and relative Bishop Burnet. Both Dr. Arbuthnot and Sir Hans Sloane, we may remark in passing, have given evidence in favour of the purer living. His own diet he thus describes in his Author’s Case, written towards the end of his life:— “My regimen, at present, is milk, with tea, coffee, bread and butter, mild cheese, salads, fruits and seeds of all kinds, with tender roots (as potatoes, turnips, carrots), and, in short, everything that has not life, dressed or not, as I like it, in which there is as much or a greater variety than in animal foods, so that the stomach need never be cloyed. I drink no wine nor any fermented liquors, and am rarely dry, most of my food being liquid, moist, or juicy.[141] Only after dinner I drink either coffee or green tea, but seldom both in the same day, and sometimes a glass of soft, small cider. The thinner my diet, the easier, more cheerful and lightsome I find myself; my sleep is also the sounder, though perhaps somewhat shorter than formerly under my full animal diet; but then I am more alive than ever I was. As soon as I wake I get up. I rise commonly at six, and go to bed at ten.” As for the effect of this regimen, he tells us that “since that time [his last lapse] I thank God I have
- 58. gone on in one constant tenor of diet, and enjoy as good health as, at my time of life (being now sixty), I or any man can reasonably expect.” When we remember the complicity of maladies of which he had been the victim during his adhesion to the orthodox mode of living, such experience is sufficiently significant. Some ten years later he records his experiences as follows:— “It is now about sixteen years since, for the last time, I entered upon a milk and vegetable diet. At the beginning of this period, this light food I took as my appetite directed, without any measures, and found myself easy under it. After some time, I found it became necessary to lessen this quantity, and I have latterly reduced it to one-half, at most, of what I at first seemed to bear; and if it should please God to spare me a few years longer, in order to preserve, in that case, that freedom and clearness which by his presence I now enjoy, I shall probably find myself obliged to deny myself one-half of my present daily sustenance, which, precisely, is three Winchester pints of new milk, and six ounces of biscuit, made without salt or yeast, baked in a quick oven.”[142]— [Natural Method of Curing Diseases, &c., page 298; see also Preface to Essay on Regimen]. The last production of Dr. Cheyne was his “Natural Method of Curing the Diseases of the Body, and the Disorders of the Mind Depending on the Body. In three parts. Part I.—General Reflections on the Economy of Nature in Animal Life. Part II.—The Means and Methods for Preserving Life and Faculties;
- 59. and also Concerning the Nature and Cure of Acute, Contagious, and Cephalic Disorders. Part III.— Reflections on the Nature and Cure of Particular Chronic Distempers. 8vo. Strahan, London, 1742.” It is dedicated to the celebrated Lord Chesterfield, who records his grateful recognition of the benefits he had experienced from his methods. He writes: “I read with great pleasure your book, which your bookseller sent me according to your direction. The physical part is extremely good, and the metaphysical part may be so too, for what I know, and I believe it is, for as I look upon all metaphysics to be guess work of imagination, I know no imagination likelier to hit upon the right than yours, and I will take your guess against any other metaphysician’s whatsoever. That part which is founded upon knowledge and experience I look upon as a work of public utility, and for which the present age and their posterity may be obliged to you, if they will be pleased to follow it.” Lord Chesterfield, it will be seen below, was one of those more refined minds whose better conscience revolted from, even if they had not the courage or self-control to renounce, the Slaughter House. The Natural Method its author considers as a kind of supplement to his last book, containing “the practical inferences, and the conclusions drawn from
- 60. [its principles], in particular cases and diseases, confirmed by forty years’ experience and observation.” It is the most practical of all his works, and is full of valuable observations. Very just and useful is his rebuke of that sort of John-Bullism which affects to hold “good living” not only as harmless but even as a sort of merit— “How it may be in other countries and religions I will not say, but among us good Protestants, abstinence, temperance, and moderation (at least in eating), are so far from being thought a virtue, and their contrary a vice, that it would seem that not eating the fattest and most delicious, and to the top, were the only vice and disease known among us—against which our parents, relatives, friends, and physicians exclaim with great vehemence and zeal. And yet, if we consider the matter attentively we shall find there is no such danger in abstinence as we imagine, but, on the contrary, the greatest abstinence and moderation nature and its external laws will suffer us to go into and practise for any time, will neither endanger our health, nor weaken our just thinking, be it ever so unlimited or unrestrained.... And it is a wise providence that Lent time falls out at that season which, if kept according to its original intention, in seeds and vegetables well dressed and not in rich high-dressed fish, would go a great way to preserve the health of the people in general, as well as dispose them to seriousness and reflection—so true it is that ‘godliness has the promise of this life, and of that which is to come,’ and it is very observable that in all civil and established religious worships hitherto known among polished nations Lents, days of abstinence, seasons of fasting and bringing down the brutal part of the rational being, have had a large share, and been reckoned an indispensable part of their
- 61. worship and duty, except among a wrong-headed part of our Reformation, where it has been despised and ridiculed into a total neglect. And yet it seems not only natural and convenient for health, but strongly commended both in the Old and New Testament, and might allow time and proper disposition for more serious and weighty purposes. And this ‘Lent,’ or times of abstinence, is one reason of the cheerfulness or serenity of some Roman Catholic or Southern countries, which would be still more healthy and long-lived were it not for their excessive use of aromatics and opiates, which are the worst kind of dry drams, and the cause of their unnatural and unbridled lechery and shortness of life.” Denouncing the general practice of the Profession of encouraging their patients in indulging vitiated habits and tastes, he reminds them:— “That such physicians do not consider that they are accountable to the community, to their patients, to their conscience, and to their Maker, for every hour and moment they shorten and cut off their patients’ lives by their immoral and murderous indulgence: and the patients do not duly ponder that suicide (which this is in effect) is the most mortal and irremissible of all sins, and neither have sufficiently weighed the possibility that the patient, if not quickly cut off by both these preposterous means, may linger out miserably, and be twenty or thirty years a-dying, under these heart and wheel-breaking miseries thus exasperated; whereas, by the methods I propose, if they obtain not in time a perfect cure, yet they certainly lessen their pain, lengthen their days, and continue under the benign influence of ‘the Sun of Righteousness, who has healing in His wings,’ and, at worst, soften and lighten the anguish of their dissolution, as far as the nature of things will admit.”
- 62. Not the least useful and instructive portions of his treatise are his references to the proper regimen for mental diseases and disordered brains, which, he reasonably infers, are best treated by the adoption of a light and pure dietary. He despairs, however, of the general recognition, or at least adoption, of so rational a method by the “faculty” or the public at large, “Who do not consider that nine parts in ten of the whole mass of mankind are necessarily confined to this diet (of farinacea, fruits, &c.), or pretty nearly to it, and yet live with the use of their senses, limbs, and faculties, without diseases or with but few, and those from accidents or epidemical causes; and that there have been nations, and now are numbers of tribes, who voluntarily confine themselves to vegetables only, ... and that there are whole villages in this kingdom whose inhabitants scarce eat animal food or drink fermented liquors a dozen times a year.” In regard to all nervous and brain diseases, he insists that the reformed diet would “Greatly alleviate and render tolerable original distempers derived from diseased parents, and that it is absolutely necessary for the deep-thinking part of mankind, who would preserve their faculties ripe and pregnant to a green old age and to the last dregs of life; and that it is the true and real antidote and preservative from wrong-headedness, irregular and disorderly intellect and functions, from loss of the rational faculties, memory, and senses, as far as the ends of
- 63. Providence and the condition of mortality will allow.”—(Nat. Method, page 90.) This benevolent and beneficent dietetic reformer, according to the testimony of an eye-witness, exemplified by his death the value of his principles— relinquishing his last breath easily and tranquilly, while his senses remained entire to the end. During his last illness he was attended by the famous David Hartley, noticed below. He was buried at Weston, near Bath. His character is sufficiently seen in his writings which, if they contain some metaphysical or other ideas which our reason cannot always endorse, in their practical teaching prove him to have been actuated by a true and earnest desire for the best interests of his fellow-men. One of the merits of Cheyne’s writings is his discarding the common orthodox esoteric style of his profession, who seem jealously to exclude all but the “initiated” from their sacred mysteries. One of his biographers has remarked upon this point that “there is another peculiarity about most of Dr. Cheyne’s writings which is worthy of notice. Although there are many passages that are quite unintelligible to the reader unless he possesses a considerable knowledge, not only of medicine but also of mathematics, yet there is no doubt but that the greater part of his works were intended for popular perusal, and in this
- 64. undertaking he is one of the few medical writers who have been completely successful. His productions, which were much read and had an extensive influence in their day, procured him a considerable degree of reputation, not only with the public, but also with the members of his own profession. If they present to the reader no great discoveries (?) they possess the merit of putting more prominently forward some useful but neglected truths; and though now, probably, but little read, they contain much matter that is well worth studying, and have obtained for their author a respectable place in the history of medical literature.”[143] Our notice of the author of the Essay on Regimen, &c., would scarcely be complete without some reference to his friendship with two distinguished characters—John Wesley and Samuel Richardson,[144] the author of Pamela. It was to Dr. Cheyne that Wesley, as he tells us in his journals, was indebted for his conversion to those dietetic principles to which he attributes, in great measure, the invigoration of his naturally feeble constitution, and which enabled him to undergo an amount of fatigue and toil, both mentally and bodily, seldom or never surpassed. Of Cheyne’s friendship for Richardson there are several memorials preserved in his familiar letters to that popular writer; and his free
- 65. and naïve criticisms of his novels are not a little amusing. The novelist, it seems, was one of his patients, and that he was not always a satisfactory one, under the abstemious regimen, appears occasionally from the remonstrances of his adviser.
- 66. XX. POPE. 1688–1744. THE most epigrammatic, and one of the most elegant, of poets. He was also one of the most precocious. His first production of importance was his Essay on Criticism, written at the age of twenty-one, although not published until two years later. But he had composed, we are assured, several verses of an Epic at the age of twelve; and his Pastorals was given to the world by a youth of sixteen. Its division into the Four Seasons is said to have suggested to Thomson the title of his great poem. The MS. passed through the hands of some distinguished persons, who loudly proclaimed the merits of the boy-poet. In the same year with his fine mock-heroic Rape of the Lock (1712) appeared The Messiah, in imitation of Isaiah and of Virgil (in his well-known Eclogue IV.), both of whom celebrate, in similar strains, the advent of a “golden age” to be. The “Sybilline” prophecy, which Pope supposes the Latin poet to have read, existed, it need scarcely be
- 67. added, only in the imagination of himself and of the authorities on whom he relied. Windsor Forest (1713) deserves special notice as one of the earliest of that class of poems which derive their inspiration directly from Nature. It was the precursor of The Seasons, although the anti-barbarous feeling is less pronounced in the former. We find, however, the germs of that higher feeling which appears more developed in the Essay on Man; and the following verses, descriptive of the usual “sporting” scenes, are significant:—
- 68. “See! from the brake the whirring Pheasant springs, And mounts exulting on triumphant wings: Short is his joy; he feels the fiery wound, Flutters in blood, and panting beats the ground. Ah, what avail his glossy, varying dyes, His purple crest and scarlet-circled eyes— The vivid green his shining plumes unfold, His painted wings, and breast that flames with gold? * * * * * * * * To plains with well-breathed beagles they repair, And trace the mazes of the circling Hare. Beasts, urged by us, their fellow-beasts pursue, And learn of man each other to undo. With slaughtering guns the unwearied fowler roves, When frosts have whitened all the naked groves, Where Doves, in flocks, the leafless trees o’ershade, And lonely Woodcocks haunt the watery glade— He lifts the tube, and level with his eye, Straight a short thunder breaks the frozen sky. Oft, as in airy rings they skim the heath, The clamorous Lapwings feel the leaden death: Oft, as the mounting Larks their notes prepare, They fall and leave their little lives in air.” His Epistle of Eloisa to Abelard (a romantic version of a very realistic story), Temple of Fame, Imitations of Chaucer, translation of the Iliad (1713– 1720)—characterised by Gibbon as having “every merit but that of likeness to its original”—an edition of Shakspere, The Dunciad (1728), translation of the Odyssey, are some of the works which attest his genius and industry. But it is with his Moral Essays—
- 69. and in particular the Essay on Man (1732–1735), the most important of his productions—that we are especially concerned. As is pretty well known, these Essays owe their conception, in great part, to his intimate friend St. John Bolingbroke. Although the author by birth and, perhaps, still more from a feeling of pride which might make him reluctant to abandon an unfashionable sect (such it was at that time), belonged nominally to the Old Church, the theology and metaphysics of the work display little of ecclesiastical orthodoxy. The pervading principles of the Essay on Man are natural theology or, as Warburton styles it, “Naturalism” (i.e., the putting aside human assertion for the study of the attributes of Deity through its visible manifestations) and Optimism.[145] The merits of the Essay, it must be added, consist not so much in the philosophy of the poem as a whole as in the many fine and true thoughts scattered throughout it, which the author’s epigrammatic terseness indelibly fixes in the mind. Of the whole poem the most valuable part, undoubtedly, is its ridicule of the common arrogant (pretended) belief that all other species on the earth have been brought into being for the benefit of the human race —an egregious fallacy, by the way, which, ably
- 70. exposed as it has been over and over again, still frequently reappears in our popular theology and morals. To the writers and talkers of this too numerous class may be commended the rebukes of Pope:— “Nothing is foreign—parts relate to whole: One all-extending, all-preserving soul Connects each being, greatest with the least— Made beast in aid of man, and man of beast: All served, all serving—nothing stands alone. * * * * * * * Has God, thou fool, worked solely for thy good, Thy joy, thy pastime, thy attire, thy food? * * * * * * * Is it for thee the Lark ascends and sings? Joy tunes his voice, joy elevates his wings. Is it for thee the Linnet pours his throat? Loves of his own and raptures swell the note. The bounding Steed you pompously bestride Shares with his lord the pleasure and the pride. * * * * * * * Know Nature’s children all divide her care, The fur that warms a monarch warmed a Bear. While Man exclaims, ‘See all things for my use!’ ‘See Man for mine!’ replies a pampered Goose. And just as short of reason he must fall, Who thinks all made for one, not one for all.” He then paints the picture of the “Times of Innocence” of the Past, or rather (as we must take it) of the Future:—
- 71. “No murder clothed him, and no murder fed. In the same temple—the resounding wood— All vocal beings hymned their equal God. The shrine, with gore unstained, with gold undrest, Unbribed, unbloody, stood the blameless priest. Heaven’s attribute was universal care, And man’s prerogative to rule but spare. Ah, how unlike the man of times to come— Of half that live the butcher and the tomb! Who, foe to Nature, hears the general groan, Murders their species, and betrays his own. But just disease to luxury succeeds, And every death its own avenger breeds: The fury-passions from that blood began, And turned on man a fiercer savage, man.” Again, depicting the growth of despotism and superstition, and speculating as to— “Who first taught souls enslaved and realms undone The enormous faith of Many made for One?” he traces the gradual horrors of sacrifice beginning with other, and culminating in that of the human, species:—
- 72. “She [Superstition] from the rending earth and bursting skies Saw gods descend, and fiends infernal rise: Here fixed the dreadful, there the blest, abodes— Fear made her devils and weak Hope her gods— Gods partial, changeful, passionate, unjust, Whose attributes were rage, revenge, or lust— Such as the souls of cowards might conceive, And, formed like tyrants, tyrants would believe. * * * * * * * * Altars grew marble then, and reeked with gore; Then first the Flamen tasted living food, Next his grim idol smeared with human blood. With Heaven’s own thunders shook the earth below, And played the God an engine on his foe.” Whenever occasion arises, Pope fails not to stigmatise the barbarity of slaughtering for food; and the sæva indignatio urges him to upbraid his fellows with the slaughter of— “The lamb thy riot dooms to bleed, * * * * * * * Who licks the hand just raised to shed his blood.” And, again, he expresses his detestation of the selfishness of our species who— “Destroy all creatures for their sport or gust.”
- 73. That all this was no mere affectation of feeling appears from his correspondence and contributions to the periodicals of the time:— “I cannot think it extravagant,” he writes, “to imagine that mankind are no less, in proportion, accountable for the ill use of their dominion over the lower ranks of beings, than for the exercise of tyranny over their own species. The more entirely the inferior creation is submitted to our power, the more answerable we must be for our mismanagement of them; and the rather, as the very condition of Nature renders them incapable of receiving any recompense in another life for ill- treatment in this.”[146] Consistently with the expression of this true philosophy, he declares elsewhere that— “Nothing can be more shocking and horrid than one of our kitchens sprinkled with blood, and abounding with the cries of expiring victims, or with the limbs of dead animals scattered or hung up here and there. It gives one the image of a giant’s den in romance, bestrewed with scattered heads and mangled limbs.”[147] The personal character of Pope, we may add, has of late been subjected to minute and searching criticism. Some meannesses, springing from an extreme anxiety for fame with after ages, have undoubtedly tarnished his reputation for candour. His excessive animosity towards his public or private enemies may be palliated in part, if not excused, by
- 74. his well-known feebleness of health and consequent mental irritability. For the rest, he was capable of the most sincere and disinterested attachments; and not his least merit, in literature, is that in an age of servile authorship he cultivated literature not for place or pay, but for its own sake. Amongst Pope’s intimate friends were Dr. Arbuthnot, Dean Swift, and Gay. The first of these, best known as the joint author with Pope and Swift of Martinus Scriblerus, a satire on the useless pedantry prevalent in education and letters, and especially as the author of the History of John Bull (the original of that immortal personification of beef, beer, and prejudice), published his Essay Concerning Aliments, in which the vegetable diet is commended as a preventive or cure of certain diseases, about the year 1730. Not the least meritorious of his works was an epitaph on the notorious Colonel Chartres—one of the few epitaphs which are attentive less to custom than to truth, and, we may add, in marked contrast with that typical one on his unhistorical contemporary Captain Blifil. In the Travels of Lemuel Gulliver the reader will find the sæva indignatio of Swift—or, at all events, of
- 75. the Houyhnhnms—amongst other things, launched against the indiscriminating diet of his countrymen:— “I told him” [the Master-Horse], says Gulliver, “we fed on a thousand things which operated contrary to each other—that we eat when we are not hungry, and drink without the provocation of thirst ... that it would be endless to give him a catalogue of all diseases incident to human bodies, for they could not be fewer than five or six hundred, spread over every limb and joint—in short, every part, external and intestine, having diseases appropriated to itself—to remedy which there was a sort of people bred up among us in the profession or pretence of curing the sick.” Among the infinite variety of remedies and prescriptions, in the human Materia Medica, the astounded Houyhnhnm learns, are reckoned “serpents, toads, frogs, spiders, dead men’s flesh and bones, birds, beasts, fishes”—no mere travellers’ tales (it is perhaps necessary to explain), but sober fact, as any one may discover for himself by an examination of some of the received and popular medical treatises of the seventeenth century, in which the most absurd “prescriptions,” involving the most frightful cruelty, are recorded with all seriousness:— “My master, continuing his discourse, said there was nothing that rendered the Yahoos more odious than their undistinguishing appetite to devour everything that came in their way, whether herbs, roots, berries, the corrupted flesh
- 76. of animals, or all mingled together; and that it was peculiar in their temper that they were fonder of what they could get by rapine or stealth at a greater distance than much better food provided for them at home. If their prey held out, they would eat till they were ready to burst.” Although unaccustomed to the better living, and finding it “insipid at first,” the human slave of the Houyhnhnm (a word which, by the way, in that language, means “the perfection of nature”) records as the result of his experience, in the first place, how little will sustain human life; and, in the second place, the fact of the superior healthfulness of the vegetable food.[148] About this period or a little earlier, Philippe Hecquet, a French physician, published his Traité des Dispenses du Carême (“Treatise on Dispensations in Lent”), 1709, in which he gave in his adhesion to the principles of Vegetarianism—at all events, so far as health is concerned. He is mentioned by Voltaire, and is supposed to be the original of the doctor Sangrado of Le Sage.[149] If this conjecture have any truth, the author of Gil Blas is open to the grave charge of misrepresentation, of sacrificing truth to effect, or (what is still worse and still more common) of pandering to popular prejudices.[150]
- 77. XXI. THOMSON. 1700–1748. IN the long and terrible series of the Ages the distinguishing glory of the eighteenth century is its Humanitarianism—not visible, indeed, in legislation or in the teaching of the ordinarily-accredited guides of the public faith and morals, but proclaimed, nevertheless, by the great prophets of that era. As far as ordinary life was concerned, the last age is only too obnoxious to the charge of selfishness and heartlessness. Callousness to suffering, as regards the non-human species in particular, is sufficiently apparent in the common amusements and “pastimes” of the various grades of the community. Yet, if we compare the tone of even the common- place class of writers with that of the authors of quasi-scientific treatises of the preceding century—in which the most cold-blooded atrocities on the helpless victims of human ignorance and barbarity are prescribed for the composition of their medical nostrums, &c., with the most unconscious audacity
- 78. and ignoring of every sort of feeling—considerable advance is apparent in the slow onward march of the human race towards the goal of a true morality and religion. To the author of The Seasons belongs the everlasting honour of being the first amongst modern poets earnestly to denounce the manifold wrongs inflicted upon the subject species, and, in particular, the savagery inseparable from the Slaughter-House—for Pope did not publish his Essay on Man until four years after the appearance of Spring. James Thomson, of Scottish parentage, came to London to seek his fortune in literature, at the age of 25. For some time he experienced the poverty and troubles which so generally have been the lot of young aspirants to literary, especially poetic, fame. Winter—which inaugurated a new school of poetry— appeared in March, 1726. That the publisher considered himself liberal in offering three guineas for the poem speaks little for the taste of the time; but that a better taste was coming into existence is also plain from the fact of its favourable reception, notwithstanding the obscurity of the author. Three editions appeared in the same year. Summer, his next venture, was published in 1727, and the (Four)
- 79. Seasons in 1730, by subscription—387 subscribers enrolling their names for copies at a guinea each. Natural enthusiasm, sympathy, and love for all that is really beautiful on Earth (a sort of feeling not to be appreciated by vulgar minds) forms his chief characteristic. But, above all, his sympathy with suffering in all its forms (see, particularly, his reflections after the description of the snowstorm in Winter), not limited by the narrow bounds of nationality or of species but extended to all innocent life—his indignation against oppression and injustice, are what most honourably distinguish him from almost all of his predecessors and, indeed, from most of his successors. The Seasons is the forerunner of The Task and the humanitarian school of poetry. The Castle of Indolence in the stanza of Spenser, has claims of a kind different from those of The Seasons; and the admirers of The Faerie Queen cannot fail to appreciate the merits of the modern romance. Besides these chefs-d’œuvre Thomson wrote two tragedies, Sophonisba and Liberty, the former of which, at the time, had considerable success upon the stage. In the number of his friends he reckoned Pope and Samuel Johnson, both of whom are said to have had some share in the frequent revisions which he made of his principal production.
- 80. It is with his Spring that we are chiefly concerned, since it is in that division of his great poem that he eloquently contrasts the two very opposite diets. Singing the glories of the annual birth-time and general resurrection of Nature, he first celebrates “The living Herbs, profusely wild, O’er all the deep-green Earth, beyond the power Of botanist to number up their tribes, (Whether he steals along the lonely dale In silent search, or through the forest, rank With what the dull incurious weeds account, Bursts his blind way, or climbs the mountain-rock, Fired by the nodding verdure of its brow). With such a liberal hand has Nature flung Their seeds abroad, blown them about in winds, Innumerous mixed them with the nursing mould, The moistening current and prolific rain. But who their virtues can declare? Who pierce, With vision pure, into those secret stores Of health and life and joy—the food of man, While yet he lived in innocence and told A length of golden years, unfleshed in blood? A stranger to the savage arts of life— Death, rapine, carnage, surfeit, and disease— The Lord, and not the Tyrant, of the world.” And then goes on to picture the feast of blood:—
- 81. “And yet the wholesome herb neglected dies, Though with the pure exhilarating soul Of nutriment and health, and vital powers Beyond the search of Art, ’tis copious blessed. For, with hot ravin fired, ensanguined Man Is now become the Lion of the plain And worse. The Wolf, who from the nightly fold Fierce drags the bleating Prey, ne’er drank her milk, Nor wore her warming fleece; nor has the Steer, At whose strong chest the deadly Tiger hangs, E’er ploughed for him. They, too, are tempered high, With hunger stung and wild necessity, Nor lodges pity in their shaggy breast. But Man, whom Nature formed of milder clay, With every kind emotion in his heart, And taught alone to weep; while from her lap She pours ten thousand delicacies—herbs And fruits, as numerous as the drops of rain Or beams that gave them birth—shall he, fair form, Who wears sweet smiles and looks erect on heaven, E’er stoop to mingle with the prowling herd And dip his tongue in gore? The beast of prey, Blood-stained, deserves to bleed. But you, ye Flocks, What have you done? Ye peaceful people, what To merit death? You who have given us milk In luscious streams, and lent us your own coat Against the winter’s cold? And the plain Ox, That harmless, honest, guileless animal, In what has he offended? He, whose toil, Patient and ever ready, clothes the land With all the pomp of harvest—shall he bleed, And struggling groan beneath the cruel hands E’en of the clowns he feeds, and that, perhaps, To swell the riot of the autumnal feast W b hi l b ?”[151]
- 82. Won by his labour?”[151] And again in denouncing the amateur slaughtering (euphemised by the mocking term of Sport) unblushingly perpetrated in the broad light of day:— “When beasts of prey retire, that all night long, Urged by necessity, had ranged the dark, As if their conscious ravage shunned the light, Ashamed. Not so [he reproaches] the steady tyrant Man, Who with the thoughtless insolence of Power, Inflamed beyond the most infuriate wrath Of the worst monster that e’er roamed the waste, For Sport alone pursues the cruel chase, Amid the beamings of the gentle days. Upbraid, ye ravening tribes, our wanton rage, For hunger kindles you, and lawless want; But lavish fed, in Nature’s bounty rolled— To joy at anguish, and delight in blood— Is what your horrid bosoms never knew.”[152] We conclude these extracts from The Seasons with the poet’s indignant reflection upon the selfish greed of Commerce, which barbarously sacrifices by thousands (as it does also the innocent mammalia of the seas) the noblest and most sagacious of the terrestrial races for the sake of a superfluous luxury: —
- 83. “Peaceful, beneath primeval trees, that cast Their ample shade o’er Niger’s yellow stream, And where the Ganges rolls his sacred waves; Or mid the central depth of blackening woods, High raised in solemn theatre around, Leans the huge Elephant, wisest of brutes! O truly wise! with gentle might endowed: Though powerful, not destructive. Here he sees Revolving ages sweep the changeful Earth, And empires rise and fall: regardless he Of what the never-resting race of men Project. Thrice happy! could he ’scape their guile Who mine, from cruel avarice, his steps: Or with his towering grandeur swell their state— The pride of kings!—or else his strength pervert, And bid him rage amid the mortal fray, Astonished at the madness of mankind.”[153]
- 84. Welcome to our website – the perfect destination for book lovers and knowledge seekers. We believe that every book holds a new world, offering opportunities for learning, discovery, and personal growth. That’s why we are dedicated to bringing you a diverse collection of books, ranging from classic literature and specialized publications to self-development guides and children's books. More than just a book-buying platform, we strive to be a bridge connecting you with timeless cultural and intellectual values. With an elegant, user-friendly interface and a smart search system, you can quickly find the books that best suit your interests. Additionally, our special promotions and home delivery services help you save time and fully enjoy the joy of reading. Join us on a journey of knowledge exploration, passion nurturing, and personal growth every day! ebookbell.com