Go Tutorial

Go Home

Go Basics

Go Variables

Go Literals

Go Type Handling

Go Type Conversion

Go Operators

Go Decision Making

Go Loops

Go Functions

Go String

Go Strings

Go Arrays

Go Slices

Go Maps

Go Pointers

Golang Reference

Golang Programs

Golang Practice

Golang Miscellaneous

Home » Golang

Go main() and init() function

Last Updated : July 21, 2025

In Go, every executable program must have a main() function defined in the main package. This is the entry point of the program. Additionally, Go provides an init() function which is automatically executed before the main() function. The init() function is commonly used to perform setup tasks like initializing variables or configurations.

The main() Function

The main() function is where the execution of a Go program begins. It must be defined in the main package.

Example

This example defines a basic main() function:

package main
import "fmt"

func main() {
    fmt.Println("Hello from main!")
}

When you run the above code, the output will be:

Hello from main!

The init() Function

The init() function runs automatically before the main() function. It’s useful for initialization logic and can be declared multiple times across different files within the same package.

Example

This example shows how init() executes before main():

package main
import "fmt"

func init() {
    fmt.Println("Initialization in progress...")
}

func main() {
    fmt.Println("Program starts now.")
}

When you run the above code, the output will be:

Initialization in progress...
Program starts now.

Multiple init() Functions

You can define multiple init() functions in different files of the same package. They will run in the order the files are compiled, not the order they are written.

Example

Here’s an example with two init() functions in one file:

package main
import "fmt"

func init() {
    fmt.Println("First init function")
}

func init() {
    fmt.Println("Second init function")
}

func main() {
    fmt.Println("Main function")
}

When you run the above code, the output will be:

First init function
Second init function
Main function

Difference Between main() and init() Functions

The main() and init() functions serve different purposes in a Go program, and understanding their differences is key to managing program execution flow effectively:

Point	Description
main() Function	The `main()` function is mandatory in every executable Go program, as it serves as the program's entry point.
init() Invocation	The `init()` function runs automatically before the `main()` function and is invoked by the Go runtime.
Multiple init() Functions	There can be multiple `init()` functions spread across different files in the same package, and all of them will be executed.
init() Signature	The `init()` function does not take any arguments and does not return any value.