Feat: made syncbeacon always shutdown (#898)

Co-authored-by: Hans Moog <hm@mkjc.net>

plugins/syncbeacon/plugin.go

@@ -64,7 +64,10 @@ func configure(_ *node.Plugin) {
 }
 
 // broadcastSyncBeaconPayload broadcasts a sync beacon via communication layer.
-func broadcastSyncBeaconPayload() {
+func broadcastSyncBeaconPayload() (doneSignal chan struct{}) {
+	doneSignal = make(chan struct{}, 1)
+	go func() {
+		defer close(doneSignal)
 
 		syncBeaconPayload := payload.NewSyncBeaconPayload(clock.SyncedTime().UnixNano())
 		msg, err := issuer.IssuePayload(syncBeaconPayload)
@@ -75,6 +78,9 @@ func broadcastSyncBeaconPayload() {
 		}
 
 		log.Debugf("issued sync beacon %s", msg.ID())
+	}()
+
+	return
 }
 
 func run(_ *node.Plugin) {
@@ -83,10 +89,17 @@ func run(_ *node.Plugin) {
 		defer ticker.Stop()
 		for {
 			select {
+			case <-shutdownSignal:
+				return
 			case <-ticker.C:
-				broadcastSyncBeaconPayload()
+				doneSignal := broadcastSyncBeaconPayload()
+
+				select {
 				case <-shutdownSignal:
 					return
+				case <-doneSignal:
+					// continue with the next beacon
+				}
 			}
 		}
 	}, shutdown.PrioritySynchronization); err != nil {