Coding in GO - GDG SL - NSBM

coding in GO
Monthly meetup November 2015 NSBM
Raveen Perera

History
Created by Robert Griesemer, Rob Pike, Ken Thompson
Developed in 2007 and first stable open source release 2009 (BSD)
GO
Fast, compiled language, directly to machine code and spearheaded by

What’s so special about GO ?
Compilation
Very fast compilation (seconds)
No VM needed
GOs Assembler
Tools
go fmt go vet
go test go doc
Concurrency
Asynchronous processes called
GOroutines
Channels used to pass data
between routines
Standard Library
net/http
flag
encoding/json encoding/xml
Simplicity in Syntax
GO stands between C and Python
Highly influenced by many other
popular programming languages
Deployment
Can be compiled to a single binary
file
You can build and compile in your
host or server

Download and install GO
https://golang.org/dl/
Download and install Sublime Text 3
http://www.sublimetext.com/3
and install GOSublime plugin
https://github.com/DisposaBoy/GoSublime

package main
import (
"fmt"
)
func main() {
fmt.Println("Hello World!")
}
$ go run helloworld.go

The Basics
https://golang.org/ref/spec
Variables
var age int = 40
name := “John Doe”
const pi float64 = 3.14
strings “ ” or ` `
bool true false
+ - * / %
&& || ! == != >= <=

Loops
for i := 0; i < count; i++ {
}
for i, value := range array {
}
for i <= 10 {
i++
}

Conditions
if i > 10 {
} else if i > 5 {
} else {
}
switch grade {
case 75: fmt.Println("A")
default: fmt.Println("nothing")
}

Arrays
var myArray[5] int
myArray := [5]int {1,2,3,4,5}
mySlice := []int {1,2,3,4,5} //Slice has no size declaration
mySlice2 := mySlice[3:5]
slice := make([]int, 5, 10)
slice = append(slice,0,1)

Maps
Just like dictionaries in python
grades := make(map[string] int)
grades[“John”] = 80
delete(grades,”John”)

Functions
func myFunc(number int) int {
return number + 5
}
func myFunc(number int) (int,int) {
return number + 5, number +6
}
Executes after the enclosing function
defer myFunc()
Undefined number of variables
func uParams(args ...int) int {
}

func divide(num1 int, num2 int) int {
defer func() {
fmt.Println(recover())
}()
answer := num1/ num2
return answer
}
func divide() {
defer func() {
fmt.Println(recover())
}()
panic(“sending to recover”)
}
Functions - defer() and panic()

Closure
Declaring a function inside another
func main() {
myfunc := func() int {}
myfunc()
}

Pointers
x := 8
changeX(&x)
func changeX(x *int){
*x = 10
}
myPointer := new(int)
X
memory address
(0xc0820022b0)

Structures
Go is not object oriented
type Circle struct {
var radius float64
var name string
}
myCircle = Circle{name:”circle1” , radius:5}
func (circle Circle) area() float64 {
return circle.radius*circle.radius*3.14
}

Handling Concurrency
GORoutines
Not expensive as threads
Multiple Goroutines without cost
Channels
GORoutines reads and writes values from an to
channels to communicate
https://golang.org/pkg/sync/atomic/

GO http
Route
Handles the requests and determines which function should
handle that request
Handler
The function that executes when a request is made
Server
The networking code which handles the requests and routes
(Serve mux) multiplexer, http request router

Simple http server
Simple respond writer
package main
import "net/http"
func main() {
http.HandleFunc("/", homeHandler)
http.ListenAndServe(":8100", nil)
}
func homeHandler(w http.ResponseWriter, r *http.Request) {
w.Write([]byte("අ◌ායුෙබ◌ා◌් වන්"))
}

Gorilla Toolkit
Gorilla Mux
$ go get github.com/gorilla/mux
simple buffer writer
Gorilla sessions
$ go get github.com/gorilla/sessions

GO Frameworks Toolkits and Micro Frameworks
https://github.com/golang/go/wiki/LearnServerProgramming

Who uses Go
https://github.com/golang/go/wiki/GoUsers

Thank You
Monthly meetup November 2015 NSBM
Raveen Perera

Coding in GO - GDG SL - NSBM

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