Add watch options

mdns.go

@@ -297,8 +297,14 @@ func (m *mdnsRegistry) ListServices() ([]*registry.Service, error) {
 	return services, nil
 }
 
-func (m *mdnsRegistry) Watch() (registry.Watcher, error) {
+func (m *mdnsRegistry) Watch(opts ...registry.WatchOption) (registry.Watcher, error) {
+	var wo registry.WatchOptions
+	for _, o := range opts {
+		o(&wo)
+	}
+
 	md := &mdnsWatcher{
+		wo:   wo,
 		ch:   make(chan *mdns.ServiceEntry, 32),
 		exit: make(chan struct{}),
 	}

watcher.go

@@ -9,6 +9,7 @@ import (
 )
 
 type mdnsWatcher struct {
+	wo   registry.WatchOptions
 	ch   chan *mdns.ServiceEntry
 	exit chan struct{}
 }
@@ -26,6 +27,12 @@ func (m *mdnsWatcher) Next() (*registry.Result, error) {
 				continue
 			}
 
+			// Filter watch options
+			// wo.Service: Only keep services we care about
+			if len(m.wo.Service) > 0 && txt.Service != m.wo.Service {
+				continue
+			}
+
 			var action string
 
 			if e.TTL == 0 {