The Go features I can't live without, 2nd round
- 1. The Go features I can't live without, 2nd round Golang Brno meetup #2 16 June 2016 Rodolfo Carvalho Red Hat
- 2. Previously goo.gl/ZkHw4X 1. Simplicity 2. Single dispatch 3. Capitalization 4. gofmt 5. godoc 6. No exceptions 7. Table-Driven Tests 8. Interfaces
- 3. 9
- 4. First-class functions In Go, functions are rst-class citizens. They can be taken as argument, returned as value, assigned to variables, and so on. Trivial, but not all languages have it... Bash nightmares! You know what, you can even implement methods on function types! //FromGo'snet/http/server.go typeHandlerFuncfunc(ResponseWriter,*Request) func(fHandlerFunc)ServeHTTP(wResponseWriter,r*Request){ f(w,r) }
- 6. 10
- 7. Fully quali ed imports Easy to tell where a package comes from. packagebuilder import( "fmt" "io/ioutil" "os" "os/exec" "time" "github.com/docker/docker/builder/parser" kapi"k8s.io/kubernetes/pkg/api" "github.com/openshift/origin/pkg/build/api" "github.com/openshift/origin/pkg/client" )
- 8. Compare with Ruby require'rubygems' require'openshift-origin-node/model/frontend/http/plugins/frontend_http_base' require'openshift-origin-node/utils/shell_exec' require'openshift-origin-node/utils/node_logger' require'openshift-origin-node/utils/environ' require'openshift-origin-node/model/application_container' require'openshift-origin-common' require'fileutils' require'openssl' require'fcntl' require'json' require'tmpdir' require'net/http' Now we need a way to determine where each of those things come from.
- 9. Imports in Go Plain strings, give exibility to language spec. "The interpretation of the ImportPath is implementation-dependent but it is typically a substring of the full le name of the compiled package and may be relative to a repository of installed packages." Path relative to GOPATH. PackageName != ImportPath; by convention, the package name is the base name of its source directory. Making imports be valid URLs allows tooling (goget) to automate downloading dependencies. Note: fully quali ed imports doesn't solve package versioning.
- 10. 11
- 11. Static typing with type inference Stutter-fee static typing Let the compiler type check, not unit tests Easier refactorings cmd:=exec.Command("yes") varcmd=exec.Command("yes") varcmd*exec.Cmd=exec.Command("yes") varcmd*exec.Cmd cmd=exec.Command("yes")
- 12. 12
- 13. Speed Development Compilation Execution Just a super cial reason to justify Go's success.
- 14. What I like Go is a compiled language that feels like scripting*. Minimal boilerplate: No need* for con g les, build scripts, header les, XML les, etc. The only con guration is GOPATH. * But not all the time... E.g., big projects like OpenShift can take 330+s to build with Go 1.6 ☹
- 16. How it improved over time 40 30 20 10 0 Speed (m/s) 1.0 2.0 3.0 4.0 5.0 6.0 Time (s)
- 17. 13
- 18. Metaprogramming Wikipedia says: ... the writing of computer programs with the ability to treat programs as their data. It means that a program could be designed to read, generate, analyse or transform other programs, and even modify itself while running. Go has no support for generics, at least yet. No macros. But has: re ect package. Packages in the stdlib for parsing, type checking and manipulating Go code. Go programs that write Go programs and can serve as example: gofmt, goimports, stringer, gofix, etc. gogeneratetool.
- 19. 14
- 20. Static linking The linker creates statically-linked binaries by default. Easy to deploy/distribute. Big binary sizes. OpenShift is a single binary with 134 MB today. Includes server, client, numerous command line tools, Web Console, ... Tale: distributing a Python program.
- 21. 15
- 22. Cross-compilation Develop/build on your preferred platform, deploy anywhere. Operating Systems: Linux OS X Windows *BSD, Plan 9, Solaris, NaCl, Android Architectures: amd64 x86 arm, arm64, ppc64, ppc64le, mips64, mips64le
- 23. Easy to use $GOOS=linux GOARCH=armGOARM=7gobuild-ofunc-linux-arm7 func.go $GOOS=linux GOARCH=armGOARM=6gobuild-ofunc-linux-arm6 func.go $GOOS=linux GOARCH=386 gobuild-ofunc-linux-386 func.go $GOOS=windowsGOARCH=386 gobuild-ofunc-windows-386func.go $filefunc-* func-linux-386: ELF32-bitLSBexecutable,Intel80386,version1(SYSV), staticallylinked,notstripped func-linux-arm6: ELF32-bitLSBexecutable,ARM,EABI5version1(SYSV), staticallylinked,notstripped func-linux-arm7: ELF32-bitLSBexecutable,ARM,EABI5version1(SYSV), staticallylinked,notstripped func-windows-386:PE32executable(console)Intel80386(strippedtoexternal PDB),forMSWindows $dufunc-* 2184 func-linux-386 2188 func-linux-arm6 2184 func-linux-arm7 2368 func-windows-386
- 24. 16
- 25. Go Proverbs Similar to The Zen of Python, there is a lot of accumulated experience and shared knowledge expressed by Go Proverbs. Not actually a feature, but a "philosophical guidance".
- 26. Go Proverbs 1/4 Don't communicate by sharing memory, share memory by communicating. Concurrency is not parallelism. Channels orchestrate; mutexes serialize. The bigger the interface, the weaker the abstraction. Make the zero value useful.
- 27. Go Proverbs 2/4 interface{} says nothing. Gofmt's style is no one's favorite, yet gofmt is everyone's favorite. A little copying is better than a little dependency. Syscall must always be guarded with build tags. Cgo must always be guarded with build tags.
- 28. Go Proverbs 3/4 Cgo is not Go. With the unsafe package there are no guarantees. Clear is better than clever. Re ection is never clear. Errors are values.
- 29. Go Proverbs 4/4 Don't just check errors, handle them gracefully. Design the architecture, name the components, document the details. Documentation is for users. Don't panic.
- 30. Recap 9. First-class functions 10. Fully quali ed imports 11. Static typing with type inference 12. Speed 13. Metaprogramming 14. Static linking 15. Cross-compilation 16. Go Proverbs
- 31. Thank you Rodolfo Carvalho Red Hat rhcarvalho@gmail.com http://rodolfocarvalho.net