About the use of go modules environment construction and package management tools

1 GOPATH

• Go Dependency management of has mainly experienced 3 Stages , Namely GOPATH, GoVendor, Go Module.

• The whole evolution route is mainly developed iteratively around the realization of two goals , Namely 1,2

• GOPATH yes Go An environment variable supported by the language ,value yes Go Project workspace .
  The directory has the following structure :
  src Deposit Go Project source code ;
  pkg: Store the intermediate products of compilation , Speed up compilation ;
  bin: Deposit Go The second lecture system file generated by the project compilation .
  

• use gopath What are the disadvantages of relying on Management ? I believe everyone has their own thinking results , Let me have a look , The same ke , Yes 2 A version ,A->A468, B-EC0 and src There can only be one version under ,AB There is no guarantee that it will compile , That is to say gopath Under management , If there are multiple projects that depend on this library, it is the same code , Different projects cannot rely on different versions of the same library , This obviously does not meet our project dependency requirements . To solve this problem ,govender There is .

#  Enter the following command on the command line to view Go Configuration information 
go env

GOARCH Represents the target processor architecture .
GOBIN Indicates where the compiler and linker are installed .
GOOS Represents the target operating system .
GOPATH Represents the current working directory .
GOROOT Express Go Installation directory of development package .

How to modify GOPATH
windows default directory %USERPROFILE%\go
Add, delete, modify and check directly in the environment variable .

2 GoVendor

• Vendor Is a directory in the current project , It stores the version of the current project . stay Vendor Hu zhixia , If the current project exists Vendor Catalog , The dependencies in this directory will be used preferentially , If dependency does not exist , From (GOHATH Search for ）

3 Go Module

• GoModues yes Go The dependency management system officially launched by the language , It solves the problems existing in the previous dependency management system, such as being unable to rely on multiple versions of the same library go mocdue from Go 11.1 Start experimental introduction ,Go 1.16 Default on ;

 How to view Go edition 
go version

• Set up go mod and go proxy
  go env -w The configuration will be written to GOENV=“/Users/youdi/Library/Application Support/go/env”

Go Modules Environment configuration 
go env -w GOBIN=/Users/gwj11/go/bin
go env -w GO111MODULE=on
go env -w GOPROXY=https://goproxy.cn,direct //  Use seven cow cloud 

• GO111MODULE=off,go The command line will not support module function , Looking for dependency packages will follow the old version through vendor Catalog or GOPATH Pattern to find .
  GO111MODULE=on,go Command guild Use modules, And not at all GOPATH Directory lookup .
  When modules When the function is enabled , The storage location of the dependency package is changed to $GOPATH/pkg, Allow the same package Multiple versions coexist , And multiple projects can share the cache module

4 An example

First, we need to initialize a go.mod

go mod init test

Then when we introduce the module , With test( Define... At initialization time ) start , Then connect the module path , such as

import "test/module"

Create a new one hello.go The documents are as follows

package main

import "github.com/astaxie/beego"

func main() {
    
    beego.Run()
}

Follow past practice , To run hello.go You need to perform go get command download beego Package to $GOPATH/src
Now we can directly go run hello.go
Wait a moment … go Will automatically find the package in the code , Download dependency package , And write specific dependencies and versions to go.mod and go.sum In file .

module Gone

go 1.14

require github.com/gin-gonic/gin v1.6.3

see go.mod, It's going to be like this ：

module hello

go 1.12

require github.com/astaxie/beego v1.11.1

• Where are the dependent packages downloaded ？ still GOPATH Li ？
  be not in . Use Go Package management mode of , The dependent third party package has been downloaded to $GOPATH/pkg/mod