The range keyword in go is used to turn something into “an iterable”. Calling it an “iterable” is my invention. Anyways, it’s used to turn a variety of data structures into something you can loop over.

A simple example

package main

import "fmt"

func main() {

    nums := []int{2, 3, 4}
    sum := 0
    // loop over a slice of numbers
    for _, num := range nums {
        sum += num
    }
    fmt.Println("sum:", sum)

    // loop over a map
    kvs := map[string]string{"a": "apple", "b": "banana"}
    for k, v := range kvs {
        fmt.Printf("%s -> %s\n", k, v)
    }

    //loop over a string
    for i, c := range "go" {
        fmt.Println(i, c)
    }
}