For

for is Go’s only looping construct. Here are some basic types of for loops.

package main

import "fmt"

func main() {

    // The most basic type, with a single condition.
    i := 1
    for i <= 3 {
        fmt.Println(i)
        i = i + 1
    }

    // A classic initial/condition/after for loop.
    for j := 7; j <= 9; j++ {
        fmt.Println(j)
    }

    // for without a condition will loop repeatedly
    // until you break out of the loop
    // or return from the enclosing function.
    for {
        fmt.Println("loop")
        break
    }

    // You can also continue to the next iteration of the loop.
    for n := 0; n <= 5; n++ {
        if n%2 == 0 {
            continue
        }
        fmt.Println(n)
    }
}

$ go run for.go
1
2
3
7
8
9
loop
1
3
5

We’ll see some other for forms later when we look at range statements, channels, and other data structures.