Loops in Go: A Practical Guide with Examples

Go has only one looping keyword: for. That can look unusual if you come from a language with separate for, while, and do-while constructs, but Go’s for is flexible enough to cover the common looping patterns.

1. Basic for Loop

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

This is similar to a traditional loop in C, Java, or JavaScript: initialize a counter, continue while the condition is true, and run the post statement after each iteration.

2. Use for Like a while Loop

Omit the initialization and post statement:

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

3. Infinite Loops

A for statement without a condition runs indefinitely until something exits the loop:

i := 0
for {
    fmt.Println(i)
    i++
    if i >= 5 {
        break
    }
}

4. Iterate over Collections with range

Array or slice:

numbers := []int{1, 2, 3}
for index, value := range numbers {
    fmt.Printf("%d: %d\n", index, value)
}

Map:

people := map[string]int{"Alice": 30, "Bob": 25}
for key, value := range people {
    fmt.Printf("%s: %d\n", key, value)
}

Map iteration order is not guaranteed, so do not depend on keys being returned in a particular sequence.

String:

message := "Hi"
for index, r := range message {
    fmt.Printf("%d: %c\n", index, r)
}

When ranging over a string, Go iterates over Unicode code points (rune values). The index is the byte offset, not necessarily a character count.

5. Nested Loops

for i := 1; i <= 3; i++ {
    for j := 1; j <= 3; j++ {
        fmt.Printf("i=%d, j=%d\n", i, j)
    }
}

6. Control Loop Execution

Use:

• break to leave the current loop.
• continue to skip directly to the next iteration.

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

Conclusion

Although Go has only one looping construct, it handles counted loops, condition-based loops, infinite loops, and iteration over arrays, slices, maps, strings, and channels. Learning the different forms of for is enough to cover nearly every ordinary iteration task in Go.