GODRIVER-2730 Remove blocking channel in update recovering. (#1196)

Author: qingyang-hu

x/mongo/driver/topology/server.go

@@ -473,19 +473,11 @@ func (s *Server) update() {
 	checkNow := s.checkNow
 	done := s.done
 
-	var doneOnce bool
 	defer func() {
-		if r := recover(); r != nil {
-			if doneOnce {
-				return
-			}
-			// We keep this goroutine alive attempting to read from the done channel.
-			<-done
-		}
+		_ = recover()
 	}()
 
 	closeServer := func() {
-		doneOnce = true
 		s.subLock.Lock()
 		for id, c := range s.subscribers {
 			close(c)