Go: How to manage the local submodule without URL like “github.com~~”

The best practice I found

1. Create project like following.

myapp/main.go

   package main

   import (
       "fmt"
        hello "myapp/hello"
   )

   func main() {
       fmt.Println("Module Test")
          hello.Hello()
   }

1. Create myapp/hello/hello.go

   package hello

   import "fmt"

   func Hello() {
      fmt.Println("Test")
   }

1. Build dependency files.

$ go mod init myapp
$ go run main.go

1. You can get go.mod and go.sum . Keep go.mod and go.sum under version control.

Why it works?

Generally, Go assumes that all modules will be served via git repository or service like github. Yes, it’s big revolution. Because it’s the main stream that uses the open source module via git hosting service like github.com.

But there are exceptions. If you need to build the home brew application in your private business with the private git hosting service e.g. gitlab or github enterprise, you don’t need to use the module name with git hosting service like github.com.

In this case, I used the latest module management rule of Go. How you can locate your source code outside of GOPATH. So any module can be linked outside of GOPATH.

To guide the localtion of modules, we used go.mod and generated this file by using go mod init myapp.

Should I keep go.mod and go.sum under version control?

My answer is YES. In 1st time, you don’t have go.mod and go.sum . Then you need to run go mod init myapp . go.mod file has all version info of your dependencies and go.sum is a checksum of dependencies.

In some case, the latest dependency can have a problem like missing modules or bugs. Then you need go.mod file to assign the right version of a dependency.

When we should activate GO1111MOULE ?

According to golang wiki, _GO111MODULE is used when you work under GOPATH.

Note that outside of GOPATH, you do not need to set GO111MODULE to activate module mode. Alternatively, if you want to work in your GOPATH:

$ export GO111MODULE=on                         # manually active module mode
$ cd $GOPATH/src/<project path>                 # e.g., cd $GOPATH/src/you/hello

Reference

• How to define a module

Thanks to

• Sangkil,he gave the idea of this article.