event, whisper/whisperv6: use defer where possible (#20940)

Author: ucwong

event/event.go

@@ -196,9 +196,9 @@ func (s *TypeMuxSubscription) closewait() {
 	s.closed = true
 
 	s.postMu.Lock()
+	defer s.postMu.Unlock()
 	close(s.postC)
 	s.postC = nil
-	s.postMu.Unlock()
 }
 
 func (s *TypeMuxSubscription) deliver(event *TypeMuxEvent) {

whisper/whisperv6/whisper.go

@@ -340,11 +340,11 @@ func (whisper *Whisper) getPeers() []*Peer {
 	arr := make([]*Peer, len(whisper.peers))
 	i := 0
 	whisper.peerMu.Lock()
+	defer whisper.peerMu.Unlock()
 	for p := range whisper.peers {
 		arr[i] = p
 		i++
 	}
-	whisper.peerMu.Unlock()
 	return arr
 }