How to Create Package in Go: Simple Guide for Beginners

In Go, you create a package by placing your Go files in a folder with a package declaration at the top. Use package packagename to name it, then import it in other files with import "packagename" to use its functions or types.

Syntax

To create a package in Go, start your Go file with the package keyword followed by the package name. This name is how other files will refer to it. For example:

• package packagename: Declares the package name.
• Functions or variables declared after belong to this package.
• Files in the same folder should share the same package name.

go

package packagename

func Hello() string {
    return "Hello from package"
}

Example

This example shows how to create a package named greetings with a function, then use it in the main package.

go

// greetings/greetings.go
package greetings

func Hello() string {
    return "Hello, Go packages!"
}

// main.go
package main

import (
    "fmt"
    "greetings"
)

func main() {
    message := greetings.Hello()
    fmt.Println(message)
}

Output

Hello, Go packages!

Common Pitfalls

Some common mistakes when creating packages in Go include:

• Using different package names in files within the same folder.
• Not exporting functions or variables (names must start with a capital letter to be accessible outside the package).
• Incorrect import paths, especially when using modules.

Example of wrong and right usage:

go

// Wrong: function not exported (starts with lowercase)
package greetings

func hello() string {
    return "hello"
}

// Right: function exported (starts with uppercase)
package greetings

func Hello() string {
    return "hello"
}

Quick Reference

Concept	Description
package packagename	Declares the package name at the top of Go files
Exported names	Start with uppercase to be accessible outside the package
Import path	Use import statement with package path to use it
Folder structure	Files in the same folder share the same package name
main package	Special package where program execution starts

Key Takeaways

Start Go files with 'package packagename' to create a package.

Export functions by capitalizing their names to use them outside the package.

Keep all files in the same folder under the same package name.

Import packages using their folder or module path to access their code.

The 'main' package is special and runs your program's entry point.