Go Break

Summary: in this tutorial, you will learn how to use the Go break statement to exit a loop prematurely.

Introduction to the Go break statement

In Go, the break statement allows you to exit a loop prematurely:

breakCopy

Typically, you terminate the loop based on a condition, therefore, you often use the break with an if statement like this:

if condition {
   break
}Copy

For example, the following shows how to use the break statement to terminate a loop that finds the first occurrence of the letter o in the string "Hello World":

package main

import "fmt"

func main() {
	messages := "Hello World"
	for index, value := range messages {
		if value == 'o'  {
			fmt.Printf("The letter o found at the index %d\n", index)
			break
		}
	}
}Copy

How it works.

First, declare a message variable and initialize its value to "Hello World":

messages := "Hello World"Copy

Second, iterate over each character in the string messages using a for range loop:

for index, value := range messages {Copy

Third, display the index of the first occurrence of the letter o and terminate the loop prematurely using the break statement:

if value == 'o'  {
	fmt.Printf("The letter o found at the index %d\n", index)
	break
}Copy

If we don’t use the break statement, the for range loop will run till the last character of the string Hello World.

Using Go break statement with a label

The break statement accepts an optional loop label:

break LoopLabelCopy

In practice, you use the break statement with a label when you want to stop inner and outer loops. For example:

package main

import "fmt"

func main() {
	matrix := [][] int {
		{1, 2, 3},
		{4, 5, 6},
		{7, 5, 5},
	}
		
    target := 5

    search:
    for i := 0; i < len(matrix); i++ {
        for j := 0; j < len(matrix[i]); j++ {
            if matrix[i][j] == target {
                fmt.Printf("Found %d at (%d, %d)\n", target, i, j)
                break search
            }
        }
    }
}Copy

How it works.

First, declare and initialize a two-dimensional array:

matrix := [][] int {
    {1, 2, 3},
    {4, 5, 6},
    {7, 5, 5},
}Copy

Second, declare and initialize a variable that holds a value to search:

target := 5Copy

Third, iterate over the elements of the matrix using two for loops to find the number 5:

search:
for i := 0; i < len(matrix); i++ {
	for j := 0; j < len(matrix[i]); j++ {
    	if matrix[i][j] == target {
        	fmt.Printf("Found %d at (%d, %d)\n", target, i, j)
            break search
        }
    }
}Copy

Before the loop, we declare the search label for using with the break statement. Inside the loops, when we come across an element with the value 5, we stop both inner and outer loops using the break search statement.

Summary

• Use the break statement to terminate a loop immediately.