Importing package from different module locally in Go (Golang)

There are cases when we want to import a module which is present locally. Let’s understand how we can import such module. But first, we have to create a module that can be used by others and then import it into the other module. For that let’s create two modules

sample.com/math module
school module

school module will be calling code of the sample.com/math module

Let’s first create the sample.com/math module which will be used by school module

Make a math directory

Create a module with an import path as sample.com/math

go mod init sample.com/math

Create a file math.go with the below contents in the math directory

package math

func Add(a, b int) int {
	return a + b
}

Now let’s create the school module

Create a school directory in the same path as the math directory side by side
Create a module name school

go mod init school

Now let’s modify the go.mod file to import the math module in the school module. To import a local module that is not pushed to VCS, we are going to use the replace directory. The replace directory will replace the module path with the path you specify.

module school

go 1.14

replace sample.com/math => ../math

Create file school.go which is going to use the Add function in sample.com/math module

package main

import (
	"fmt"
	"sample.com/math"
)

func main() {
	fmt.Println(math.Add(2, 4))
}

Now do a go run

go run school.go

It is able to call the Add function of the sample.com/math module and correctly gives the output as 6.

Also, it will update the go.mod with version information of the sample.com/math module

module school

go 1.14

replace sample.com/math => ../math

require sample.com/math v0.0.0-00010101000000-000000000000

golang