code: func IsRFC1918(na *wire.NetAddress) bool {
  	for _, rfc := range rfc1918Nets {
  		if rfc.Contains(na.IP) {
  			return true
  		}
  	}
  	return false
  }
docs: // IsRFC1918 returns whether or not the passed address is part of the IPv4
  // private network address space as defined by RFC1918 (10.0.0.0/8,
  // 172.16.0.0/12, or 192.168.0.0/16).