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Go For Loop: One Loop To Rule Them All

Loops are an important concept in programming, and Go has several options for looping through code. Unlike other programming languages, Go only has one keyword to create a loop: for.

That doesn’t mean Go has just one type of loop, though. In this article, we’ll explore four ways of looping in Go: for loops, while loops, infinite loops, and looping over a range.

The syntax of a Go for loop

One type of loop in Go is the for loop. It closely resembles the traditional for-loop that those with experience in C-like languages will know. It has three parts:

  1. the init statement,
  2. the condition,
  3. and the post statement.

The init statement runs at the beginning of the loop, the condition is checked before each iteration, and the post statement runs at the end of each iteration. Here’s an example:

for i := 0; i < 5; i++ {
    fmt.Println(i)
}Code language: Go (go)

This loop will print out the numbers 0 through 4.

Did you recognize the three parts?

  1. The variable i is initialized to 0 in the init statement
  2. The loop continues as long as i is less than 5 (the condition)
  3. At the end of each iteration, i is incremented by 1 using the post statement i++.

A Go While Loop

Another type of loop in Go is the while loop, which only has a condition checked at the beginning of each iteration. If the condition is true, the loop continues; if it is false, it ends. Let’s see how we can create the equivalent of a while loop using for:

x := 0
for x < 5 {
    fmt.Println(x)
    x++
}Code language: Go (go)

This loop will also print out the numbers 0 through 4. The variable x is initialized to 0 before the loop, and the loop continues as long as x is less than 5. At the end of each iteration, x is incremented by 1.

Infinite loop

To create an infinite loop in Go, use for without anything else:

for {
  ....
}Code language: Go (go)

You’ll have to break out of the loop yourself, e.g. when some condition is met. To do so, you can use either:

  1. break: a statement created to break out of loops immediately
  2. return, which returns from the function this loop is currently running in
  3. goto, which jumps to a labeled section of code.

Go range loops

Finally, there’s also a range form of the for loop in Go, which iterates over a slice or map. Here’s an example:

numbers := []int{1, 2, 3, 4, 5}
for i, number := range numbers {
    fmt.Println(i, number)
}Code language: Go (go)

This loop will print out the index and value of each element in the numbers slice. The variable i is the current element’s index, and number is the value of the element.

Learn more

Here are some more resources to learn about loops: