Go step on the pit - no required module provides package: go mod file not found in current directory or any parent

background

Prepare to run the following code

package main

import (
	"github.com/gin-gonic/gin"
)

func main() {
	//  Create a default routing engine 
	r := gin.Default()
	// GET： Request mode ;/hello： The path of the request 
	//  When the client uses GET Method request /hello When the path , Will execute the following anonymous function 
	r.GET("/hello", func(c *gin.Context) {
		// c.JSON： return JSON Formatted data 
		c.JSON(200, gin.H{
			"message": "Hello world!",
		})
	})
	//  start-up HTTP service , Default in 0.0.0.0:8080 Start the service 
	r.Run()
}

The result is wrong ：

no required module provides package : go.mod file not found in current directory or any parent directory;

That is to say, the package of the imported module cannot be found

Try 1：

go get -u github.com/gin-gonic/gin

There is no effect

Try 2： About golang An error is reported in the quotation of the third-party package ：no required module provides package_ Blog of programming philosophers -CSDN Blog

Online is basically this solution ： perform ：go env -w GO111MODULE=auto

But mine is already open , So exclude this solution .

Try 3： I built another project , Another running error result is found ：

1.go:4:2: no required module provides package github.com/gin-gonic/gin; to add it:
go get github.com/gin-gonic/gin

Pay attention to the difference between the two error reports , This prompt  go get github.com/gin-gonic/gin

It shows that the original project is lack of things , I compared it and found that the folder where the original project code is located is missing go.mod This file

Through research Go go.mod Detailed explanation _ The blog of Min Ming, the owner of Jiangdong flower -CSDN Blog _go.mod file

Got the solution

resolvent

Open the terminal in the error code folder , function

go mod init  New module name 

You can initialize go.mod, Run it like this

go get -u github.com/gin-gonic/gin

Just OK 了

summary

• Go.mod yes Golang1.11 The official package management tool newly introduced by the version is used to solve the problem that there is no place to record the specific version of the package , Facilitate the management of dependent packages .
• Go.mod It's really just a Modules, About Modules The official definition of is ：Modules It's related Go Bag aggregate , Is the source code exchange and version control unit .go Command direct support Modules, Including logging and parsing dependencies on other modules .Modules Replace old based on GOPATH Methods , To specify which source files to use .
• Modules And traditional GOPATH Different , It is not necessary to include, for example src,bin Such subdirectories , A source directory or even an empty directory can be used as Modules, As long as it contains go.mod file .