func (n *discovery) AddMapping(protocol string, extPort, intPort int,
	name string, lifetime time.Duration) error {
	if err := n.wait(); err != nil {
		return err
	}
	return n.found.AddMapping(protocol, extPort, intPort, name, lifetime)
}
func (n *discovery) AddMapping(protocol string, extPort, intPort int,
	name string, lifetime time.Duration) error {
	if err := n.wait(); err != nil {
		return err
	}
	return n.found.AddMapping(protocol, extPort, intPort, name, lifetime)
}
// AddMapping maps an external port to a local port for a specific
// service.