go modules


The golang 1.11 was released. This version implemented new feature “go modules”. This tool can lock dependent library version. This is similar feature as ruby bundler.

How to use

At first Initialize go.mod file.

$ go mod init your_module_name

Then go.mod file is generated.

$ ls -l

The go.mod is defined module.

$ cat go.mod
module your_module_name

Next write test code as scrape.go.

package main

import (

func main() {
    doc, err := goquery.NewDocument("https://blog.byplayer.org/")
    if err != nil {
        fmt.Print("url scarapping failed")
    doc.Find("a").Each(func(_ int, s *goquery.Selection) {
        url, _ := s.Attr("href")

Finally go run, or go build.

$ go build
# or
$ go run scrape.go

Then automatically update go.mod file to read dependent modules and added require part as below. This file includes library version. So you can make same binary using same version libraries.

module your_module_name

require (
    github.com/PuerkitoBio/goquery v1.4.1
    github.com/andybalholm/cascadia v1.0.0 // indirect
    golang.org/x/net v0.0.0-20180826012351-8a410e7b638d // indirect

before release

Before release use tidy command to clean up unused require.

$ go mod tidy

How to upgrade go.mod

If you want to upgrade all dependent libraries, you can use below command.

$ go get -u

The go.mod file is updated.

Need I add go.sum into repository?

The go.sum should be checked in along with go.mod. This is checksum of specific version. It helps you to verify library.