2.golang應用目錄結構和GOPATH概念

golang 語言有一個GOPATH的概念就是當前工做目錄

[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的概念時代碼的起始目錄，當進行go install  或者代碼級別的 import 時  默認的包搜索路徑

   一般一個代碼 應該包含  src   pkg   bin 三個目錄再GOPATH 之下

   src 爲源碼路徑 

          源碼有三個分類 

          1.聲明爲package main 的包 

go run 可直接運行
[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 會在當前目錄生成 同名二進制
[root@localhost hello]# pwd
/root/golang_test/src/github.com/leleyao/hello
[root@localhost hello]# go build github.com/leleyao/hello # 兩種指定方式
[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 會在  GOPATH  bin 下 生成 同名二進制

　　2. 一個代碼目錄下有多個文件且有文件不是 沒有func main 則執行go install 會在對應目錄生編譯過程文件

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 結尾的文件會在執行 go test 命令時進行測試

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