go learning

1. vim-go

https://github.com/fatih/vim-go-tutorial

curl -fLo ~/.vim/autoload/plug.vim --create-dirs https://raw.githubusercontent.com/junegunn/vim-plug/master/plug.vim
git clone https://github.com/fatih/vim-go.git ~/.vim/plugged/vim-go

echo "
call plug#begin()
Plug 'fatih/vim-go', { 'do': ':GoInstallBinaries' }
call plug#end()
set autowrite
"  >> ~/.vimrc 

代码质量：go vet， golint， goimports

2. 学习资料

快速入门：

https://github.com/a8m/go-lang-cheat-sheet

了解go的基础数据类型

官方文档：

spec： https://golang.org/ref/spec

go-tour: https://tour.golang.org/list

blog: https://blog.golang.org/index

深入解析Go  这本书，分析了很多特例。 值得一看。

https://tiancaiamao.gitbooks.io/go-internals/content/zh/03.6.html

Go语言圣经（中文版）

The author Brian W. Kernighan is also write the 大名鼎鼎的  <The C Programming Lanuaguage>

go入门指南

学习go语言

在线练习  https://play.golang.org/p/e81LuPO_JR

丰富的example

go web 开发

在线文档

3. 对比学习

如果熟悉C的话，可以对比学习go

4.  继承

$ cat  base.go

 package base

 type BaseT struct {
     a int
     b int
 }

 func (b *BaseT) Add() int{
     return b.a+b.b
 }

 func (b *BaseT) Sub() int {
     return b.a-b.b
 }

 type Bf interface {
     Add() int
 }

 func NewBasetT(a, b int) *BaseT{
     return &BaseT{a, b}
 }

$ cat test.go

 package main

 import (
     "fmt"
     "base"
 )

 type BaseT struct{
     base.BaseT
     a int
     b int
 }

 func (b *BaseT) Add() int{
     return b.a+b.b
 }

 func main() {
     nb := base.NewBasetT(, )
     b := &BaseT{*nb, , }
     fmt.Println(b.Add())
 }

5.  内存指针转换为 slice

var ptr unsafe.Pointer
s := ((*[1<<10]byte)(ptr))[:200]

这里数组大小其实是假的。s是一个200个元素的slice。

这种方式其实是做了内存copy

或者这种方式：

var ptr unsafe.Pointer
var s1 = struct {
    addr uintptr
    len int
    cap int
}{ptr, length, length}
s := *(*[]byte)(unsafe.Pointer(&s1))

 这种方式就是引用原内存的东西。

6. go 缺失了python的动态特性。 不过可以用reflect进行一些扩展。

http://studygolang.com/articles/4892

此外可以使用接口进行类似弱类型参数传递。

传递时需要注意的问题。

通过断言来动态获取接口类型，还是有些傻

接口实现原理， 简易介绍。还是看官方文档。

map转struct， example

json转map，可以直接看官方文档。

使用reflect来设置struc field

7. 传递接口实现多态。

接口的操作

8. 优化

map 并发优化 map的操作跟python差不多

9. disclouser in filepath.Walk

https://xojoc.pw/justcode/golang-file-tree-traversal.html

10. go 第三方库

https://golanglibs.com/top?q=process+list

11. golang re

https://golang.org/pkg/regexp/syntax/

12.    排序例子

https://gobyexample.com/sorting-by-functions

13. 循环变量快照

在5.6.1中有讲解

在循环的闭包 引用循环变量存在这个问题。

14. 排空channel

goroutine泄露(§8.4.4)

15.  内部变量不能够在函数外部被访问到

变量(§2.3.4)在没有被转义的情况下是无法在函数外部访问的

16. plugin

since go_lang 1.8, we can use rpc for plugin.

rpc plugin: https://github.com/dkiser/go-plugin-example

more explain for 1.8 plugin:

https://jeremywho.com/go-1.8---plugins/

picture show the 1.8 plugin

https://github.com/grsmv/go-plugin-example

https://github.com/vladimirvivien/go-plugin-example

more example for plugin.

https://github.com/hashicorp/go-plugin

17. testcase

https://semaphoreci.com/community/tutorials/how-to-test-in-go

https://blog.golang.org/examples

https://golang.org/pkg/testing/

18. goroutine

golang的goroutine是如何实现的

运行时启动过程

19. nested struct

https://stackoverflow.com/questions/24809235/initialize-a-nested-struct-in-golang

20. 第三方库

https://golanglibs.com/

https://github.com/avelino/awesome-go

21. string 求最大值

sort.Sort(sort.Reverse(sort.StringSlice(s)))

22. errror handling

https://blog.golang.org/error-handling-and-go

23.  golang net/http self-sign certification.

One can use generate_cert.go in crypto/tls to generate cert.pem and key.pem.

https://golang.org/pkg/net/http/#ListenAndServeTLS

24. personal experience

http://www.jianshu.com/u/1381dc29fed9  _张晓龙_  的blog不错。详细介绍了怎么写testcase。

26. net/http unix socket example

https://gist.github.com/hakobe/6f70d69b8c5243117787fd488ae7fbf2

27. golang command

http://wiki.jikexueyuan.com/project/go-command-tutorial/0.7.html

office link

28. golang.org blog

https://blog.golang.org/defer-panic-and-recover

29. grpc

chinese doc: http://doc.oschina.net/grpc?t=60133

30. protobuf

https://developers.google.com/protocol-buffers/docs/overview

install: https://github.com/google/protobuf/blob/master/src/README.md

readme: https://github.com/google/protobuf/blob/master/README.md

31. go offical RPC example

https://play.golang.org/p/4BZQbM9lNN

 package main

 import (
     "io"
     "log"
     "net/rpc"
 )

 type pipePair struct {
     reader *io.PipeReader
     writer *io.PipeWriter
 }

 func (this *pipePair) Read(p []byte) (int, error) {
     return this.reader.Read(p)
 }

 func (this *pipePair) Write(p []byte) (int, error) {
     return this.writer.Write(p)
 }

 func (this *pipePair) Close() error {
     this.writer.Close()
     return this.reader.Close()
 }

 type Serv struct {
     token string
 }

 func (this *Serv) SetToken(token string, dummy *int) error {
     this.token = token
     return nil
 }

 func (this *Serv) GetToken(dummy int, token *string) error {
     *token = this.token
     return nil
 }

 type Registrar struct {
 }

 func (this *Registrar) Register(name string, dummy *int) error {
     rpc.RegisterName(name, new(Serv))
     return nil
 }

 func server(pipes pipePair) {
     rpc.Register(new(Registrar))
     rpc.ServeConn(&pipes)
 }

 func main() {
     var token string
     var in, out pipePair
     in.reader, out.writer = io.Pipe()
     out.reader, in.writer = io.Pipe()
     go server(out)
     client := rpc.NewClient(&in)
     // Register some objects
     client.Call("Registrar.Register", "First", nil)
     client.Call("Registrar.Register", "Second", nil)
     // Assign token values individually
     client.Call("First.SetToken", "abc", nil)
     client.Call("Second.SetToken", "def", nil)
     // Now try to read them
     client.Call("First.GetToken", , &token)
     log.Printf("first token is %v", token)
     client.Call("Second.GetToken", , &token)
     log.Printf("second token is %v", token)
 }

32.  golang process drop privilege

https://play.golang.org/p/dXBizm4xl3

 package main

 import (
     "fmt"
     "net"
     "net/http"
     "os"
     "os/exec"
     "syscall"
 )

 func main() {
     if os.Getuid() ==  {
         fmt.Println("Dropping privileges...")
         if err := drop(); err != nil {
             fmt.Println("Failed to drop privileges:", err)
             os.Exit()
         }
     }

     l, err := net.FileListener(os.NewFile(, "[socket]"))
     if err != nil {
         // Yell into the void.
         fmt.Println("Failed to listen on FD 3:", err)
         os.Exit()
     }

     http.Serve(l, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
         fmt.Fprintf(w, "I am process %d running as %d/%d", os.Getpid(), os.Getuid(), os.Getgid())
     }))
 }

 func drop() error {
     l, err := net.Listen("tcp", ":80")
     if err != nil {
         return err
     }

     f, err := l.(*net.TCPListener).File()
     if err != nil {
         return err
     }

     cmd := exec.Command(os.Args[])
     cmd.ExtraFiles = []*os.File{f}
     cmd.SysProcAttr = &syscall.SysProcAttr{
         Credential: &syscall.Credential{
             Uid: ,
             Gid: ,
         },
         Setsid: true,
     }

     if err := cmd.Start(); err != nil {
         return err
     }

     fmt.Printf("Spawned process %d, exiting\n", cmd.Process.Pid)
     cmd.Process.Release()
     os.Exit()
     return nil /* unreachable */
 }

文若的python实现： https://www.ovirt.org/develop/release-management/features/infra/supervdsm-service/

in golang father to notify child: https://github.com/opencontainers/runc/blob/master/libcontainer/system/linux.go

https://github.com/mindreframer/golang-devops-stuff/blob/master/src/github.com/dotcloud/docker/vendor/src/github.com/docker/libcontainer/system/linux.go

33. // Create a timer that will kill the process

cmd.Process.Signal  http://www.darrencoxall.com/golang/executing-commands-in-go/

34. difference os.Pipe and io.Pipe 

io.Pipe: https://golang.org/pkg/io/#Pipe Pipe creates a synchronous in-memory pipe

os.Pipe: https://golang.org/pkg/os/#Pipe  Pipe returns a connected pair of Files; 

35. os signal Notify

Notify: https://golang.org/pkg/os/signal/#example_Notify

36.  tls revoke

https://github.com/cloudflare/cfssl/tree/master/revoke

37. print struct name

https://stackoverflow.com/questions/24512112/how-to-print-struct-variables-in-console

e := reflect.ValueOf(&book).Elem()

     for i := ; i < e.NumField(); i++ {
         fieldName := e.Type().Field(i).Name
         fmt.Printf("%v\n", fieldName)
     }

38. all channel exit.

https://nathanleclaire.com/blog/2014/02/15/how-to-wait-for-all-goroutines-to-finish-executing-before-continuing/

39. Singleton Pattern in Go

http://marcio.io/2015/07/singleton-pattern-in-go/