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Go 笔记: Module

发表于 更新于 分类于 阅读次数： Valine：

Understand Module in Golang.

Code example

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//hello.go
package hello

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

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

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

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//hello_test.go
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)
	}
}

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

go 1.17

require rsc.io/quote/v3 v3.1.0

require (
	golang.org/x/text v0.3.7 // indirect
	rsc.io/sampler v1.3.0 // indirect
)

Use Go Modules

What is module?

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module：a collection of Go packages
  |
go.mod:
    - module's module path
    - dependency requirements

The Running ENV for a module:

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1. outside $GOPATH/src <--
2. inside any folder     |
   with:                 |
       - go.mod -------->|

How to creating a new module:

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1. create you file.  // status: contains a package
2. cmd: go mod init scottzhang.pro/hello  // make the current directory the root of a module
3. cmd: go test  // test the module
  • Packages in subdirectories have import paths consisting of the module path plus the path to the subdirectory.
  • So you don't need to run go mod init in subdirectories.

Understand go.mod content:

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example.com/hello //main module
golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c //an example of a pseudo-version
rsc.io/quote v1.5.2
rsc.io/sampler v1.3.0

// go command maintains a file named go.sum
// containing the expected cryptographic hashes of the content of specific module versions.
// ensure that future downloads of these modules retrieve the same bits as the first download

How to import dependencies module:

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import "rsc.io/quote"
// to check  indirect dependencies
// cmd: go list -m all

How to upgrading dependencies:

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// here is a example to upgrade text and sampler
cmd: go get golang.org/x/text
cmd: go get rsc.io/sampler

Now depends on both rsc.io/quote and rsc.io/quote/v3.

why here is V3?, because:

  • Each different major version (v1, v2, and so on) of a Go module uses a different module path
  • v3 of rsc.io/quote = rsc.io/quote/v3, Know more visit here

You can have v1, v2, v3 in same module, but can't with v1.1 and v1.2

To know what new changes in new version, type go doc rsc.io/quote/v3.

Remove no need module:

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go list -m all  # check
go mod tidy  # cleans up these unused dependencies

Conclusion

  • go mod init creates a new module, initializing the go.mod file that describes it.
  • go build, go test, and other package-building commands add new dependencies to go.mod as needed.
  • go list -m all prints the current module’s dependencies.
  • go get changes the required version of a dependency (or adds a new dependency).
  • go mod tidy removes unused dependencies.

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