Go Programming - Functions

A function is a collection of code that you can call from your program. You can pass values to a function and they can return a result. They also help keep your programs organised, a function can be called multiple times and be reused in other programs.

Functions also help with security and maintenance, any improvements to a function benefits your program anywhere it is called.

Function Examples

No Return Value

This simple function prints a message.

func hello() {
	fmt.Println("Hello World!")
}

We can call the above function as follows:

	hello()

Single Return Value

The following function takes two values and returns and the area of the shape as an integer.

func myarea(width int, height int) int {
	return width * height
}

We can pass the function to a variable or use it directly:

fmt.Println("Area:", myarea(5, 5))

Multiple Return Values

A feature of Go is that a function can return more that one value, often this is used to return a boolean (true/false) of whether the function was successful and a result.

We can expand the above area function to return two integers, an area and perimeter:

func myshape(width int, height int) (int, int) {
	return (width * height), (width + height) * 2
}

We can use the above function as follows:

	area, perimeter := myshape(5, 5)
	fmt.Println("Area:", area, " Perimeter:", perimeter)

Full Program

The Go compiling guide explains the folder set up for a Go program, once that is done:

• Save the following into the project folder as area.go
• From the command line, inside the folder use go build to make your exe file.
• Run the compiled program with area

package main

import (
	"fmt"
)

// Returning no value
func hello() {
	fmt.Println("Hello World!")
}

// Returning one value
func myarea(width int, height int) int {
	return width * height
}

// Returning two values
func myshape(width int, height int) (int, int) {
	return (width * height), (width + height) * 2
}

func main() {
	hello()
	
	fmt.Println("Area:", myarea(5, 5))

	// Putting the function results into two variables
	area, perimeter := myshape(5, 5)
	fmt.Println("Area:", area, " Perimeter:", perimeter)
}

Updated (06/08/2026)