Golang for keyword

last modified May 7, 2025

This tutorial explains how to use the for keyword in Go. We'll cover loop basics with practical examples of iteration in Go programming.

The for statement is Go's only looping construct. It can be used in three forms: as a traditional for loop, while loop, and infinite loop.

In Go, for provides all looping functionality you need. It's versatile and can iterate over collections, implement condition-based loops, and create infinite loops.

Basic for loop

The traditional for loop has initialization, condition, and post statements. This example demonstrates counting from 0 to 4.

basic_for.go

package main

import "fmt"

func main() {
    for i := 0; i < 5; i++ {
        fmt.Println(i)
    }
}

The loop initializes i to 0, runs while i < 5, and increments i after each iteration. This is the most common form.

While-style for loop

Go's while loop is just a for loop with only a condition. This example shows how to implement while-loop behavior.

while_for.go

package main

import "fmt"

func main() {
    count := 0
    
    for count < 5 {
        fmt.Println(count)
        count++
    }
}

The loop continues as long as count < 5. The counter must be managed inside the loop body, similar to traditional while loops.

Infinite for loop

An infinite loop omits all three statements. This example shows how to create and break from an infinite loop.

infinite_for.go

package main

import "fmt"

func main() {
    i := 0
    
    for {
        fmt.Println(i)
        i++
        
        if i > 4 {
            break
        }
    }
}

The loop runs indefinitely until the break condition is met. This pattern is useful for servers or long-running processes.

For-range loop

The range form iterates over slices, arrays, maps, strings, or channels. This example demonstrates iterating over a slice.

range_for.go

package main

import "fmt"

func main() {
    fruits := []string{"apple", "banana", "cherry"}
    
    for index, fruit := range fruits {
        fmt.Printf("%d: %s\n", index, fruit)
    }
}

The range returns both index and value for each element. You can omit the index using _ if only the value is needed.

Nested for loops

For loops can be nested to handle multi-dimensional data structures. This example shows a multiplication table.

nested_for.go

package main

import "fmt"

func main() {
    for i := 1; i <= 3; i++ {
        for j := 1; j <= 3; j++ {
            fmt.Printf("%d * %d = %d\t", i, j, i*j)
        }
        fmt.Println()
    }
}

The outer loop controls rows while the inner loop handles columns. Each iteration of the outer loop triggers a complete inner loop cycle.

For loop with continue

The continue statement skips to the next iteration. This example skips even numbers in a loop.

continue_for.go

package main

import "fmt"

func main() {
    for i := 0; i < 10; i++ {
        if i%2 == 0 {
            continue
        }
        fmt.Println(i)
    }
}

When i is even, continue skips the print statement. Only odd numbers between 0 and 9 are printed.

Labeled for loops

Labels allow breaking or continuing outer loops from nested structures. This example demonstrates breaking from an outer loop.

labeled_for.go

package main

import "fmt"

func main() {
OuterLoop:
    for i := 0; i < 3; i++ {
        for j := 0; j < 3; j++ {
            fmt.Printf("i=%d, j=%d\n", i, j)
            
            if i == 1 && j == 1 {
                break OuterLoop
            }
        }
    }
}

The label OuterLoop: marks the outer loop. The break statement exits both loops when the condition is met.

Source

Go language specification

This tutorial covered the for keyword in Go with practical examples of different looping scenarios and patterns.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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