go的常见操作

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go的开发环境搭建：https://www.cnblogs.com/wqzn/p/11730052.html

GOROOT和GOPATH

GOROOT和GOPATH都是环境变量，

其中GOROOT是我们安装go开发包的路径，
GOPATH是存放go的代码目录，

从Go 1.8版本开始，Go开发包在安装完成后会为GOPATH设置一个默认目录，参见下表。

GOPATH在不同操作系统平台上的默认值

平台	GOPATH默认值	举例
Windows	%USERPROFILE%/go	C:\Users\用户名\go
Unix	$HOME/go	/home/用户名/go

我们只需要记住默认的GOPATH路径在哪里就可以了。

我们需要将 GOROOT下的bin目录及GOPATH下的bin目录都添加到环境变量中。

配置环境变量之后需要重启你电脑上已经打开的终端。（例如cmd、VS Code里面的终端和其他编辑器的终端）。

VSCode：

安装Go语言开发工具包

在座Go语言开发的时候为我们提供诸如代码提示、代码自动补全等功能。

Windows平台按下Ctrl+Shift+P，Mac平台按Command+Shift+P，这个时候VS Code界面会弹出一个输入框，如下图：

设置好FQ代理：

go.toolsGopath setting is not set. Using GOPATH D:\gospace
Installing 17 tools at D:\gospace\bin in module mode.
  gocode
  gopkgs
  go-outline
  go-symbols
  guru
  gorename
  gotests
  gomodifytags
  impl
  fillstruct
  goplay
  godoctor
  dlv
  gocode-gomod
  godef
  goreturns
  golint

Installing github.com/fatih/gomodifytags SUCCEEDED
Installing golang.org/x/tools/cmd/gorename SUCCEEDED
Installing github.com/josharian/impl SUCCEEDED
Installing golang.org/x/tools/cmd/guru SUCCEEDED
Installing github.com/mdempsky/gocode SUCCEEDED
Installing golang.org/x/tools/cmd/gorename SUCCEEDED
Installing github.com/uudashr/gopkgs/v2/cmd/gopkgs SUCCEEDED
Installing github.com/cweill/gotests/... SUCCEEDED
Installing github.com/fatih/gomodifytags SUCCEEDED
Installing github.com/cweill/gotests/... SUCCEEDED
Installing github.com/fatih/gomodifytags SUCCEEDED
Installing github.com/ramya-rao-a/go-outline SUCCEEDED
Installing github.com/josharian/impl SUCCEEDED
Installing github.com/josharian/impl SUCCEEDED
Installing github.com/davidrjenni/reftools/cmd/fillstruct SUCCEEDED
Installing github.com/davidrjenni/reftools/cmd/fillstruct SUCCEEDED
Installing github.com/davidrjenni/reftools/cmd/fillstruct SUCCEEDED
Installing github.com/acroca/go-symbols SUCCEEDED
Installing golang.org/x/tools/cmd/guru SUCCEEDED
Installing golang.org/x/tools/cmd/gorename SUCCEEDED
Installing github.com/haya14busa/goplay/cmd/goplay SUCCEEDED
Installing github.com/haya14busa/goplay/cmd/goplay SUCCEEDED
Installing github.com/haya14busa/goplay/cmd/goplay SUCCEEDED
Installing github.com/cweill/gotests/... SUCCEEDED
Installing github.com/fatih/gomodifytags SUCCEEDED
Installing github.com/josharian/impl SUCCEEDED
Installing github.com/davidrjenni/reftools/cmd/fillstruct SUCCEEDED
Installing github.com/haya14busa/goplay/cmd/goplay SUCCEEDED
Installing github.com/godoctor/godoctor SUCCEEDED
Installing github.com/godoctor/godoctor SUCCEEDED
Installing github.com/godoctor/godoctor SUCCEEDED
Installing github.com/godoctor/godoctor SUCCEEDED

一、file

1、go 判断文件/目录是否存在、区分文件和目录

// IsExist checks whether a file or directory exists.
// It returns false when the file or directory does not exist.
func IsExist(f string) bool {
    _, err := os.Stat(f)
    return err == nil || os.IsExist(err)
}

// IsFile checks whether the path is a file,
// it returns false when it's a directory or does not exist.
func IsFile(f string) bool {
    fi, e := os.Stat(f)
    if e != nil {
        return false
    }
    return !fi.IsDir()
}

二、日志：

0.打印日志

log.Println("---------------load config-------------------")

直接退出

引发异常，并退出
这个 panic 可以类比 python 中的 raise、java 中的 throw, 这样抛出的异常是一个堆栈信息，能够追溯代码错误的位置，这个在使用时我用着更顺手

恢复 panic 引发的异常使用 recover

func main(){
    var s sync.WaitGroup
    for i:=0;i<10;i++{
        s.Add(1)
        go func(i int){
            defer func(){
                if err := recover();err!=nil{
                    log.Println("this is error",err)
                }
                s.Done()
                log.Println(i,"is over")
            }()
            log.Panic(i,"i want panic")
        }(i)
    }
    s.Wait()
}

但是需要注意，recover 之后并不会打印 panic 的堆栈信息。

三、序列化

示例

{
    "time_out": 20,
    "user_groups": [
        {
            "server": "192.168.1.2",
            "name": "myown",
            "port": 1234,
            "password": "1234567",
            "cipher": "AEAD_CHACHA20_POLY1305",
            "time_out": 10
        }
    ]
}

代码

package main

import(
    "io/ioutil"
    "encoding/json"
    "fmt"
    "time"
)

type UserGroup struct{
    Name string `json:"name"`
    Server    string `json:"server"`
    Port int    `json:"port"`
    Password  string `json:"password"`
    Cipher    string `json:"cipher"`
    Key       string `json:"key"`
    Keygen    int    `json:"key_gen"`
    UDPTimeout    time.Duration  `json:"time_out"`
}

type Config struct {
    UserGroups []*UserGroup `json:"user_groups"`
    UDPTimeout time.Duration `json:"time_out"`
}


/**
 * @msg: 读取json 文件数据，按照参数 v 的格式解析
 * @param: fileName
 * @return: 
 */
func LoadJsonData(fileName string, v interface{}) error{
    data, err := ioutil.ReadFile(fileName)
    if err != nil{
        return err;
    }

    dataJson := []byte(data)

    if err = json.Unmarshal(dataJson, v); err != nil{
        return err
    }
    return nil
}


func main(){
    /**
     * 异常捕获
     */
    defer func() {
        if err := recover(); err != nil{
            fmt.Println("发生异常：",err)
        }
    }()
    var MConfig = &Config{}
    if err := LoadJsonData("config.json", MConfig); err != nil{
        fmt.Println("读取配置错误")
        panic(err)
    }
    fmt.Println("获取到的数据为：", *MConfig.UserGroups[0])
}