Do unlock in defer

Signed-off-by: Jean-Noël Moyne <jnmoyne@gmail.com>

server/server.go

@@ -4271,16 +4271,15 @@ func (s *Server) LDMClientByID(id uint64) error {
 	c := s.clients[id]
 	if c != nil {
 		c.mu.Lock()
+		defer c.mu.Unlock()
 		if c.opts.Protocol >= ClientProtoInfo &&
 			c.flags.isSet(firstPongSent) {
 			// sendInfo takes care of checking if the connection is still
 			// valid or not, so don't duplicate tests here.
 			c.Debugf("sending Lame Duck Mode info to client")
 			c.enqueueProto(c.generateClientInfoJSON(info))
-			c.mu.Unlock()
 			return nil
 		} else {
-			c.mu.Unlock()
 			return errors.New("ClientProtoInfo < ClientOps.Protocol or first pong not sent")
 		}
 	}