package main import (     "fmt"     "strings" ) const input = `49927398716 49927398717 1234567812345678 1234567812345670` var t = [...]int{0, 2, 4, 6, 8, 1, 3, 5, 7, 9} func luhn(s string) bool {     odd := len(s) & 1     var sum int     for i, c := range s {         if c < '0' || c > '9' {             return false         }         if i&1 == odd {             sum += t[c-'0']         } else {             sum += int(c - '0')         }     }     return sum == 0 } func main() {     for _, s := range strings.Split(input, "\n") {         fmt.Println(s, luhn(s))     } }

49927398716 true 49927398717 false 1234567812345678 false 1234567812345670 true