A loop runs a block of code repeatedly. Most languages have several loop keywords — for, while, do-while, foreach. Go has just one: for. But that single keyword covers every looping pattern you’ll ever need.

The classic for loop

The full form has three parts separated by semicolons: an init, a condition, and a post:

package main

import "fmt"

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

i = 0
i = 1
i = 2
i = 3
i = 4

What happens, step by step:

1. Init (i := 0) — runs once, before the loop starts
2. Condition (i < 5) — checked before each iteration. If false, the loop ends.
3. Body — runs while the condition is true
4. Post (i++) — runs after each iteration, before the next condition check

This is the same pattern as for in C, Java, or JavaScript — just without the parentheses.

for as a while loop

Drop the init and post and you’ve got a while loop:

// inside main()
n := 10
for n > 0 {
    fmt.Println(n)
    n--
}

10
9
8
...
1

Go doesn’t have a while keyword — for with just a condition is the equivalent.

Infinite loop

Drop the condition entirely and the loop runs forever — until you explicitly stop it:

// inside main()
count := 0
for {
    count++
    if count == 3 {
        break
    }
    fmt.Println("Iteration", count)
}
fmt.Println("Done")

Iteration 1
Iteration 2
Done

Two new keywords appeared:

• break — immediately exits the loop
• continue (which we’ll see in a moment) — skips the rest of the current iteration and goes back to the condition check

break and continue

package main

import "fmt"

func main() {
    for i := 1; i <= 10; i++ {
        if i%2 == 0 {
            continue
        }
        if i > 7 {
            break
        }
        fmt.Println(i)
    }
}

1
3
5
7

Walk through it:

• i = 1 → odd, less than 7 → print
• i = 2 → even → continue → skip to next iteration
• i = 3 → odd, less than 7 → print
• …
• i = 7 → odd, not greater than 7 → print
• i = 8 → even → continue → second if never runs
• i = 9 → odd, but 9 > 7 → break → loop exits (so i = 10 is never reached)

Subtle, right? That’s why running these examples and changing them is the only way to truly grasp loops.

Looping over a range

Often you don’t care about counter mechanics — you just want to walk through a collection. The range keyword does this:

package main

import "fmt"

func main() {
    fruits := []string{"apple", "banana", "cherry"}

    for index, fruit := range fruits {
        fmt.Println(index, fruit)
    }
}

0 apple
1 banana
2 cherry

range returns two values per iteration — the index and the value. (We’re using a slice here, which we’ll cover properly in the next section. For now, treat []string{...} as “a list of strings”.)

If you only care about the value, ignore the index with _:

// inside main()
for _, fruit := range fruits {
    fmt.Println(fruit)
}

If you only care about the index (rare, but possible):

// inside main()
for index := range fruits {
    fmt.Println(index)
}

The blank identifier _ is Go’s way of saying “I know there’s a value here but I don’t want it.” Use it whenever you need to discard something.

A practical example

Let’s combine everything we’ve learned in this section into one complete program — counting how many even numbers are between 1 and 20:

package main

import "fmt"

func main() {
    evens := 0

    for i := 1; i <= 20; i++ {
        if i%2 != 0 {
            continue
        }
        evens++
    }

    fmt.Println("There are", evens, "even numbers between 1 and 20")
}

There are 10 even numbers between 1 and 20

It uses a for loop, an if with a comparison and modulo, and continue — every concept from this section in 12 lines.

What’s next

You’ve now covered every fundamental piece of Go’s syntax: variables, types, operators, conditionals, and loops. Programs aren’t just made of single values, though — real software works with collections of data. That’s the next section: arrays, slices, maps, pointers, and structs.

If you ever need the full list of fmt format verbs, width, and flags, the fmt Printing Cheatsheet at the end of the course is the place to look.