Convert string with IPv4 address to int32 in GO language

IPv4toInt32.go

// my IPv4 parser without slices
func ip2i(s string) uint32 {
        var ip, n uint32 = 0, 0
        var r uint = 24
        for i := 0; i < len(s); i++ {
                if '0' <= s[i] && s[i] <= '9' {
                        n = n*10 + uint32(s[i]-'0')
                        if n > 0xFF {
                                //Debug.Printf("Bad IP (1) n=%d: %s\n", n, s)
                                return 0xFFFFFFFF
                        }
                } else if s[i] == '.' {
                        if r != 0 {
                                ip = ip + (n << r)
                        } else {
                                //Debug.Printf("Bad IP (2): %s\n", s)
                                return 0xFFFFFFFF
                        }
                        r = r - 8
                        n = 0
                } else {
                        //Debug.Printf("Bad IP (3): %s\n", s)
                        return 0xFFFFFFFF
                }
        }
        if r != 0 {
                //Debug.Printf("Bad IP (4): %s\n", s)
                return 0xFFFFFFFF
        }
        ip = ip + n
        return ip
}