Validating credit card numbers

luhn.go

package main

import (
	"fmt"
	"strconv"
)

func luhnCheck(cardNo int) bool {
	toStr := strconv.Itoa(cardNo)

	var cardDigits []int

	for i := range toStr {
		x, _ := strconv.Atoi(string(toStr[i]))
		cardDigits = append(cardDigits, x)
	}

	cardLen := len(cardDigits)

	var reversedDigits []int
	l := cardLen - 1

	for i := l; i > -1; i-- {
		reversedDigits = append(reversedDigits, cardDigits[i])
	}

	var oddParity int
	var evenParity int

	for i := range reversedDigits {
		if (i+1)%2 > 0 {
			oddParity += reversedDigits[i]
		} else {
			m := reversedDigits[i] * 2
			if m > 9 {
				t := strconv.Itoa(m)
				g := 0
				for i := range t {
					x, _ := strconv.Atoi(string(t[i]))
					g += x
				}
				evenParity += g

			} else {
				evenParity += m
			}
		}
	}

	total := oddParity + evenParity
	return total%10 == 0

}

func main() {
	start := "517214"
	end := "7805"
	maxNo := 9997
	total := 0

	cardNos := []int{}

	for i := 0; i <= maxNo; i++ {
		//todo bug padd numbers less that 10
		sC := start + strconv.Itoa(i) + end
		cardNo, _ := strconv.Atoi(sC)
		isValid := luhnCheck(cardNo)
		if isValid {
			cardNos = append(cardNos, cardNo)
			total += 1
		}
	}

	fmt.Println(cardNos, total)
}