[Go brain breaker for everyone] Do a IP Version validator only in bitwise

ip_version.go

package main

// IPVersion return the version of an IP (4 or 6) only by using bitwise with zero allocation.
// This implementation are 17.6% faster than no bitwise implementation but create an unreadable
// code. I challenge myself to create that only for fun. That's fun, and I wanna to store and share
// somewhere so that is it !
func IPVersion(ipStr string) (int, error) {
	var flags uint8 = 0
	for i := 0; i < len(ipStr); i++ {
		c := ipStr[i]
		flags |= ((c ^ '.') * 1) | ((c ^ ':') * 2)
	}

	if flags == 1 || flags == 2 {
		return 4 + 2*(int(flags)>>1), nil
	}

	return 0, errors.New("invalid IP address format")
}