Go programming language has gained popularity in recent years for its simplicity, speed, and reliability. One of the most powerful features of Go is its ability to create custom packages. Custom packages allow you to organize your code into reusable modules that can be easily shared across multiple projects.

In this tutorial, we will walk through the process of creating a custom package in Go programming language.


Step 1: Create a New Directory

The first step in creating a custom package in Go is to create a new directory that will hold your package files. You can create a new directory using the following command: 

mkdir mypackage


Step 2: Create a New File

The next step is to create a new file that will hold your package code. You can create a new file using the following command: 

touch mypackage/mypackage.go


Step 3: Write Package Code

In this step, you will write the code for your custom package. In this example, we will create a package that calculates the area of a rectangle.

package mypackage

func Area(width float64, height float64) float64 {
    return width * height
}

This code defines a package named "mypackage" that contains a function named "Area" that calculates the area of a rectangle based on its width and height.


Step 4: Test the Package

Before you can use your custom package in another project, you need to test it to make sure it works as expected. You can test your package using the following command:

go test mypackage

If your package passes all tests, you can move on to the next step.


Step 5: Publish the Package

Once you have tested your package and are confident that it works as expected, you can publish it to a public repository such as Github, Gitlab, or Bitbucket. To publish your package, you will need to create a new repository and push your package code to it.


Step 6: Use the Package in Another Project

To use your custom package in another project, you will need to import it using the import statement. For example, to use our "mypackage" package in another project, you would use the following code:

import "github.com/yourusername/mypackage"

func main() {
    width := 10.0
    height := 20.0
    area := mypackage.Area(width, height)
    fmt.Println(area)
}

This code imports the "mypackage" package and uses its "Area" function to calculate the area of a rectangle.


Conclusion

Creating custom packages in Go programming language is a powerful way to organize your code and make it reusable across multiple projects. By following the steps outlined in this tutorial, you can easily create, test, and publish your own custom packages in Go.