2.golang应用目录结构和GOPATH概念

golang 语言有一个GOPATH的概念就是当前工作目录

[root@localhost golang_test]# tree
.
├── bin
│   └── hello
├── first.go
├── pkg
├── README.md
├── src                          
│   └── github.com
│       └── leleyao
│           ├── hello
│           │   └── hello.go
│           ├── mymath
│           │   └── mymath.go
│           └── stringutil
│               ├── reverse.go
│               └── reverse_test.go
└── statics
    └── timg.jpg

[root@localhost golang_test]# tail -3 /etc/profile
export GOPATH=/root/golang_test
export PATH=$PATH:/go/bin
export PATH=$PATH:$(go env GOPATH)/bin      
[root@localhost golang_test]# echo $GOPATH
/root/golang_test
[root@localhost golang_test]# echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/go/bin:/root/golang_test/bin:/root/bin

　GOPATH的概念时代码的起始目录，当进行go install  或者代码级别的 import 时  默认的包搜索路径

   通常一个代码 应该包含  src   pkg   bin 三个目录再GOPATH 之下

   src 为源码路径 

          源码有三个分类 

          1.声明为package main 的包 

go run 可直接运行
[root@localhost hello]# go run hello.go 
123
0
Hello, My  lele yao !
[root@localhost hello]# cat hello.go 
package main

import (
	"fmt"

	. "github.com/leleyao/stringutil"
)

var _lele int
func main() {
	var _song int
        _song = 123
        fmt.Println(_song) 
        fmt.Println(_lele) 
	fmt.Println(Reverse("! oay elel  yM ,olleH"))
}
go build 会在当前目录生成 同名二进制
[root@localhost hello]# pwd
/root/golang_test/src/github.com/leleyao/hello
[root@localhost hello]# go build github.com/leleyao/hello # 两种指定方式
[root@localhost hello]# ls
hello  hello.go

[root@localhost hello]# go build
[root@localhost hello]# ls
hello  hello.go
[root@localhost hello]# # go install
[root@localhost hello]# ll $GOPATH/bin
total 1952
-rwxr-xr-x. 1 root root 1997543 May 23 09:51 hello


go install 会在  GOPATH  bin 下 生成 同名二进制

　　2. 一个代码目录下有多个文件且有文件不是 没有func main 则执行go install 会在对应目录生编译过程文件

ll /root/golang_test/pkg/linux_amd64/github.com/leleyao/stringutil.a 
-rw-r--r--. 1 root root 2902 May 23 13:07 /root/golang_test/pkg/linux_amd64/github.com/leleyao/stringutil.a
[root@localhost stringutil]# rm -rf /root/golang_test/pkg/linux_amd64
[root@localhost stringutil]# cat reverse.go 
// Package stringutil contains utility functions for working with strings.
package stringutil

// Reverse returns its argument string reversed rune-wise left to right.
func Reverse(s string) string {
	r := []rune(s)
	for i, j := 0, len(r)-1; i < len(r)/2; i, j = i+1, j-1 {
		r[i], r[j] = r[j], r[i]
	}
	return string(r)
}

　　3. 以_test 结尾的文件会在执行 go test 命令时进行测试

[root@localhost stringutil]# go test
PASS
ok  	github.com/leleyao/stringutil	0.003s
[root@localhost stringutil]# ls
reverse.go  reverse_test.go

golang跨平台编译

CGO_ENABLE=0 GOOS=linux GOARCH=amd64 go build 

跨平台编译是关闭C的依赖

GOOS 指定平台类型  linux window  darwin

GOARCH 指定服务器架构 amd64 arm