Go 语言：使用 mod 管理依赖

#Go 语言

go 1.11 引入了 mod 预览特性，用来管理依赖。go 1.12 正式支持。

官方介绍

示例1

$ mkdir sql2dsl
$ cd sql2dsl
$ go mod init sql2dsl
$ ls
go.mod

上面的命令中，go mod init sql2dsl 用于初始化模块。

go.mod 文件内容如下：

module sql2dsl

go 1.12

在 sql2dsl 目录中编写文件 main.go ：

package main

import (
    "fmt"
    "github.com/cch123/elasticsql"
    "github.com/tidwall/pretty"
)

var sql = `
select * from user_info
where id=1
`

func main() {
    dsl, esType, _ := elasticsql.Convert(sql)
    // 打印 type 名称
    fmt.Println(esType)
    fmt.Println()
    // 打印 dsl
    fmt.Println(dsl)
    fmt.Println()
    // 打印格式化后的 dsl
    var result = pretty.Pretty([]byte(dsl))
    fmt.Println(string(result))
}

运行：

$ go run main.go
go: finding github.com/tidwall/pretty v1.0.0
go: finding github.com/cch123/elasticsql v1.0.0
go: downloading github.com/tidwall/pretty v1.0.0
go: extracting github.com/tidwall/pretty v1.0.0
go: downloading github.com/cch123/elasticsql v1.0.0
go: extracting github.com/cch123/elasticsql v1.0.0
go: finding github.com/xwb1989/sqlparser latest
go: downloading github.com/xwb1989/sqlparser v0.0.0-20180606152119-120387863bf2
go: extracting github.com/xwb1989/sqlparser v0.0.0-20180606152119-120387863bf2
user_info

{"query" : {"bool" : {"must" : [{"match" : {"id" : {"query" : "1", "type" : "phrase"}}}]}},"from" : 0,"size" : 1}

{
  "query": {
    "bool": {
      "must": [
        {
          "match": {
            "id": {
              "query": "1",
              "type": "phrase"
            }
          }
        }
      ]
    }
  },
  "from": 0,
  "size": 1
}

第一次运行时，前面部分是下载依赖，后面是执行结果。

我们再执行一次 main.go ，不会再次下载依赖：

$ go run main.go
user_info

{"query" : {"bool" : {"must" : [{"match" : {"id" : {"query" : "1", "type" : "phrase"}}}]}},"from" : 0,"size" : 1}

{
  "query": {
    "bool": {
      "must": [
        {
          "match": {
            "id": {
              "query": "1",
              "type": "phrase"
            }
          }
        }
      ]
    }
  },
  "from": 0,
  "size": 1
}

go.sum 文件

在这个示例中，执行 main.go 之后，sql2dsl 目录下 出现了一个 go.sum 文件，内容如下：

github.com/cch123/elasticsql v1.0.0 h1:7SbQw3ZAImsajjY7lx2798n816J+rer8HrfDt4k+e8w=
github.com/cch123/elasticsql v1.0.0/go.mod h1:h4Tt1A91nOVAYsWdoxlXwKYPfxkxeTuRFkEMUQaRVBo=
github.com/tidwall/pretty v1.0.0 h1:HsD+QiTn7sK6flMKIvNmpqz1qrpP3Ps6jOKIKMooyg4=
github.com/tidwall/pretty v1.0.0/go.mod h1:XNkn88O1ChpSDQmQeStsy+sBenx6DDtFZJxhVysOjyk=
github.com/xwb1989/sqlparser v0.0.0-20180606152119-120387863bf2 h1:zzrxE1FKn5ryBNl9eKOeqQ58Y/Qpo3Q9QNxKHX5uzzQ=
github.com/xwb1989/sqlparser v0.0.0-20180606152119-120387863bf2/go.mod h1:hzfGeIUDq/j97IG+FhNqkowIyEcD88LrW6fyU3K3WqY=

记录的是版本号和哈希值。

依赖下载到哪里去了 ？

$GOPATH/pkg/mod/ 目录。

将依赖挪到本项目的 vendor 目录

$ go mod vendor

示例2

项目结构如下:

$ tree myapp
myapp
├── go.mod
├── main.go
└── utils
    └── common.go

go.mod 内容如下:

module myapp

go 1.12

utils/common.go 内容如下:

package utils

func Add(a int, b int) int {
	return a+b
}

main.go 内容如下:

package main

import "fmt"
import utils "myapp/utils"

func main() {
	fmt.Println(utils.Add(1,2))
}

运行 main.go :

$ go run main.go
3

go mod 子命令

$ go mod help
Go mod provides access to operations on modules.

Note that support for modules is built into all the go commands,
not just 'go mod'. For example, day-to-day adding, removing, upgrading,
and downgrading of dependencies should be done using 'go get'.
See 'go help modules' for an overview of module functionality.

Usage:

	go mod <command> [arguments]

The commands are:

	download    download modules to local cache
	edit        edit go.mod from tools or scripts
	graph       print module requirement graph
	init        initialize new module in current directory
	tidy        add missing and remove unused modules
	vendor      make vendored copy of dependencies
	verify      verify dependencies have expected content
	why         explain why packages or modules are needed

Use "go help mod <command>" for more information about a command.

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