Generate Random String in Golang

package main

import (
    "fmt"
    "math/rand"
)

func randomString(n int) string {
    var letters = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")

    str := make([]rune, n)
    for i := range str {
        str[i] = letters[rand.Intn(len(letters))]
    }
    return string(str)
}

func main() {
    fmt.Println(randomString(20))
}    

Output

BpLnfgDsc2WD8F2qNfHK