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Go Modules - Part 1 #5

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Go Modules - Part 1#5
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@oufeng

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@oufeng
oufeng
opened on Aug 12, 2020

  • Go 1.13及以后版本GO111MODULE=auto的行为变化。

    GO111MODULE的默认值依然为auto。但无论repo是否在GOPATH，只要目录有go.mod，go编译器都会使用go module来管理依赖

  • 如何创建模块

    新建工作区和项目文件夹

    $ mkdir -p $HOME/Desktop/go/hello
$ cd $HOME/Desktop/go/hello
$

    init mod init $path
    一是作为模块标识，二是作为模块的import path
    此时会生成go.mod文件
    当其他项目引用这个模块下的 package 时都会以该 import $path 作为共同的前缀

    $ go mod init example.com/hello
go: creating new go.mod: module example.com/hello
$ cat go.mod
module example.com/hello

go 1.15
$

    新建go文件hello.go

    package hello

func Hello() string {
    return "Hello, world."
}

    新建测试文件hello_test.go，测试是否能正常调用Hello方法

    package hello

import "testing"

func TestHello(t *testing.T) {
    want := "Hello, world."
    if got := Hello(); got != want {
        t.Errorf("Hello() = %q, want %q", got, want)
    }
}

    运行测试文件

    $ go test
PASS
ok      example.com/hello       1.221s
$

  • 如何添加依赖项

    修改hello.go。用rsc.io/quote来实现Hello

    package hello

import "rsc.io/quote"

func Hello() string {
    return quote.Hello()
}

    再次运行测试。看来Hello()方法实现了国际化功能，需要修改一下测试用例。

    ...
func TestHello(t *testing.T) {
    want := "你好，世界。"
    if got := Hello(); got != want {
        t.Errorf("Hello() = %q, want %q", got, want)
    }
}

    测试通过了，证明Hello功能正常

    $ go test
PASS
ok      example.com/hello       0.377s
$

    此时会把直接依赖写到go.mod中

    $ cat go.mod
module example.com/hello

go 1.15

require rsc.io/quote v1.5.2
$

    尝试列出目前的所有依赖。当前模块(主模块)始终是第一行，随后的才是真正的依赖关系

    $ go list -m all
example.com/hello
golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c
rsc.io/quote v1.5.2
rsc.io/sampler v1.3.0

    尝试列出所有的依赖关系。清晰明了，这个功能大赞

    $ go mod graph
example.com/hello rsc.io/quote@v1.5.2
rsc.io/quote@v1.5.2 rsc.io/sampler@v1.3.0
rsc.io/sampler@v1.3.0 golang.org/x/text@v0.0.0-20170915032832-14c0d48ead0c

    所有真正的依赖和哈希值会记录到go.sum中。哈希值的作用是确保所有依赖项不会被恶意修改。

    $ cat go.sum
golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c h1:qgOY6WgZOaTkIIMiVjBQcw93ERBE4m30iBm00nkL0i8=
golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
rsc.io/quote v1.5.2 h1:w5fcysjrx7yqtD/aO+QwRjYZOKnaM9Uh2b40tElTs3Y=
rsc.io/quote v1.5.2/go.mod h1:LzX7hefJvL54yjefDEDHNONDjII0t9xZLPXsUe+TKr0=
rsc.io/sampler v1.3.0 h1:7uVkIFmeBqHfdjD+gZwtXXI+RODJ2Wc4O7MPEh/QiW4=
rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=

  • 如何更新依赖项。版本号最好带着语义信息，v0.1.2。主要版本是0，次要版本是1，补丁版本是2

    尝试升级一下golang.org/x/text

    $ go get golang.org/x/text
go: golang.org/x/text upgrade => v0.3.3
go: downloading golang.org/x/text v0.3.3
$

    执行go list -m all并且看看go.mod和go.sum情况。
    golang.org/x/text已经升级到v0.3.3版本，go.mod也改成了golang.org/x/text v0.3.3 // indirect。
    indirect表示该依赖不是由当前项目直接依赖，而是由其他依赖包间接依赖的。

    $ go list -m all
example.com/hello
golang.org/x/text v0.3.3
golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e
rsc.io/quote v1.5.2
rsc.io/sampler v1.3.0
$ cat go.mod
module example.com/hello

go 1.15

require (
        golang.org/x/text v0.3.3 // indirect
        rsc.io/quote v1.5.2
)
$ cat go.sum
golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c h1:qgOY6WgZOaTkIIMiVjBQcw93ERBE4m30iBm00nkL0i8=
golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
golang.org/x/text v0.3.3 h1:cokOdA+Jmi5PJGXLlLllQSgYigAEfHXJAERHVMaCc2k=
golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
rsc.io/quote v1.5.2 h1:w5fcysjrx7yqtD/aO+QwRjYZOKnaM9Uh2b40tElTs3Y=
rsc.io/quote v1.5.2/go.mod h1:LzX7hefJvL54yjefDEDHNONDjII0t9xZLPXsUe+TKr0=
rsc.io/sampler v1.3.0 h1:7uVkIFmeBqHfdjD+gZwtXXI+RODJ2Wc4O7MPEh/QiW4=
rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=

    尝试升级rsc.io/sampler。发现版本太先进，兼容不了旧版本

    $ go get rsc.io/sampler
go: rsc.io/sampler upgrade => v1.99.99
go: downloading rsc.io/sampler v1.99.99
$ go test
--- FAIL: TestHello (0.00s)
hello_test.go:8: Hello() = "99 bottles of beer on the wall, 99 bottles of beer, ...", want "Hello, world."
FAIL
exit status 1
FAIL	example.com/hello	0.014s
$

    尝试列出可用的版本以及挑选一个补丁版本。go get默认是获取@latest版本

    $ go list -m -versions rsc.io/sampler    
rsc.io/sampler v1.0.0 v1.2.0 v1.2.1 v1.3.0 v1.3.1 v1.99.99
$ go get rsc.io/sampler@v1.3.1

    此时。$GOPATH/pkg/mod/rsc.io存在rsc.io/sampler的多个版本

    $ cd $HOME/go/pkg/mod/rsc.io
$ ls
quote@v1.5.2     sampler@v1.3.0   sampler@v1.3.1   sampler@v1.99.99
$

  • 如何引用同一个依赖的不同主版本

    修改hello.go。引用rsc.io/quote/v3

    package hello

import (
    "rsc.io/quote"
    quoteV3 "rsc.io/quote/v3"
)

func Hello() string {
    return quote.Hello()
}

func Proverb() string {
    return quoteV3.Concurrency()
}

    给测试文件添加以下行

    ...
func TestProverb(t *testing.T) {
    want := "Concurrency is not parallelism."
    if got := Proverb(); got != want {
        t.Errorf("Proverb() = %q, want %q", got, want)
    }
}

    再次测试一下

    $ go test
PASS
ok      example.com/hello       0.377s
$

    此时项目同时依赖rsc.io/quote和rsc.io/quote/v3

    $ go list -m rsc.io/q... 
rsc.io/quote v1.5.2
rsc.io/quote/v3 v3.1.0

    总结:

    • 主要版本不相同时要发布不同的模块，模块必须以版本号结尾
    • 相同主要版本之间要兼容
    • 像rsc.io/quote如果有多个主要版本。需要发布rsc.io/quote，rsc.io/quote/v2和rsc.io/quote/v3等模块

  • 引用同一个依赖的不同版本毕竟不是什么好事。尝试将旧的api升级到新的api，然后将旧的依赖删除。

    查看rsc.io/quote/v3版本有什么api。像是Hello升级到了HelloV3

    $ go doc rsc.io/quote/v3
package quote // import "rsc.io/quote/v3"

Package quote collects pithy sayings.

func Concurrency() string
func GlassV3() string
func GoV3() string
func HelloV3() string
func OptV3() string
$

    修改hello.go，更换一下api

    package hello

import quoteV3 "rsc.io/quote/v3"

func Hello() string {
    return quoteV3.HelloV3()
}

func Proverb() string {
    return quoteV3.Concurrency()
}

    既然没有了多个版本，可以不用alias

    package hello

import "rsc.io/quote/v3"

func Hello() string {
    return quote.HelloV3()
}

func Proverb() string {
    return quote.Concurrency()
}

    重新运行test。一切正常

    $ go test 
PASS
ok      example.com/hello       1.626s

  • 如何删除已下载但未引用的依赖。例如rsc.io/quote

    $ go list -m all
example.com/hello
golang.org/x/text v0.3.3
golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e
rsc.io/quote v1.5.2
rsc.io/quote/v3 v3.1.0
rsc.io/sampler v1.3.1

$ cat go.mod
module example.com/hello

go 1.15

require (
        golang.org/x/text v0.3.3 // indirect
        rsc.io/quote v1.5.2
        rsc.io/quote/v3 v3.1.0
        rsc.io/sampler v1.3.1 // indirect
)

    利用tidy命令删除未使用的依赖项

    $ go mod tidy
$ go list -m all
example.com/hello
golang.org/x/text v0.3.3
golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e
rsc.io/quote/v3 v3.1.0
rsc.io/sampler v1.3.1
$ cat go.mod
module example.com/hello

go 1.15

require (
        golang.org/x/text v0.3.3 // indirect
        rsc.io/quote/v3 v3.1.0
        rsc.io/sampler v1.3.1 // indirect
)

    重新测试

    $ go test
PASS
ok      example.com/hello       3.088s

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