How to install Gin with Golang

Question

I'm a newbie on Golang, and I'm trying to use Gin to develop a web server on Ubuntu 16.04.

After executing go get -u github.com/gin-gonic/gin, many folders appear at ~/go/pkg/mod/github.com/.

Then I try to make an example:

package main

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

func main() {
    r := gin.Default()
    r.GET("/ping", func(c *gin.Context) {
        c.JSON(200, gin.H{
            "message": "pong",
        })
    })
    r.Run() // listen and serve on 0.0.0.0:8080 (for windows "localhost:8080")
}

However, go run example.go made the error:

example.go:3:8: cannot find package "github.com/gin-gonic/gin" in any of:
        /usr/local/go/src/github.com/gin-gonic/gin (from $GOROOT)
        /home/zyh/go/src/github.com/gin-gonic/gin (from $GOPATH)

In my system, $GOROOT is /usr/local/go/ and $GOPATH is ~/go/.

How could I solve this problem?

Answer 1

For Go version 1.11 or newer, You should use Go Modules.

If you are just starting with Go, you should start with the newer version. I think you are using a Go version that supports go modules already because the modules you are trying to get are downloading to ~/go/pkg/mod/ directory.

To initialize a project with go module, run:

go mod init your-project-name

This will create a go.mod file in your project directory.

Add missing and/or remove unused modules:

go mod tidy

This will fill up the go.mod file with appropriate modules and create a go.sum in your project directory. The go.sum contains expected cryptographic hashes of each module version.

After that, the go run example.go command should run the program without any issues.

---

You can even vendor the modules in your project directory:

go mod vendor

This will bring all the vendors to your projects /vendor directory so that you don't need to get the modules again if working from another machine on this project.