for Loops & range

Go is refreshingly minimal: there is exactly one loop keyword, for , and it covers every job — counted loops, while-style loops, infinite loops, and (with range ) walking over slices, maps and strings. Master these forms and you can iterate over anything.

Learn for Loops & range in our free Go course — a beginner-friendly interactive lesson with worked examples, a practice exercise and a quick recall.

Part of the free Go course at LearnCodingFast — hands-on lessons with examples you run in your browser, plus practice exercises and a quick quiz.

What You'll Learn in This Lesson

1️⃣ One Keyword, Three Shapes

Every for in Go is a variation on the same keyword. The full form has three parts separated by semicolons: an init statement, a condition , and a post statement. Drop the init and post and you have a while loop. Drop everything and you have an infinite loop you exit with break .

2️⃣ break, continue & Nesting

break leaves the loop immediately; continue skips the rest of the current iteration and jumps to the next. Loops nest freely — an outer loop for rows, an inner loop for columns. (Go also supports labelled breaks to exit an outer loop from inside an inner one, which you'll meet later.)

3️⃣ range — Walk Any Collection

range is how you iterate collections idiomatically. Over a slice it yields the index and the value ; over a map it yields the key and value (in random order, by design — never rely on map order); over a string it yields the byte index and the rune . When you don't need the index or key, discard it with the blank identifier _ .

Your turn — make a countdown with a three-part loop that decrements.

Now find the best score with a range loop. You don't need the index here.

These lines sum a slice with range , but they're scrambled. Put them in order so the program prints 6 (assume a func main wraps them).

Why: you must create the slice and the accumulator ( total := 0 ) before the loop can use them. The for header opens the block, the body total += n runs once per element, the brace closes the loop, and only then can you print the final total: 1+2+3 = 6.

Predict the output before you reveal the answer.

012 — i runs 0, 1, 2 and stops when i reaches 3 because the condition i < 3 is then false.

0 a1 b — range yields index 0 with "a", then index 1 with "b". (Println-style spacing: each pair prints with a space between i and v.)

{'for i := 1; i <= 4; i++ { if i == 2 ; fmt.Print(i) }'}

134 — when i is 2, continue skips the print and moves to the next iteration, so 2 is omitted.

Go doesn't have one — a for with only a condition is a while loop: for x < 10 {' '} . One keyword, fewer surprises.

Q: Why does my map print in a different order each run?

Go deliberately randomizes map iteration order so you never accidentally rely on it. If you need a fixed order, collect the keys into a slice and sort them first.

Q: Can I loop a fixed number of times without a counter variable?

In Go 1.22+ yes: for range 5 {' '} runs five times. On older versions use a three-part loop and ignore the counter.

Range over the string, inspect each rune, and tally the vowels. Write it yourself and match the example output.

Practice quiz

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