app/platform: fix an issue about accessing to a closed db on shutdown (#21549)

app/server.go

@@ -706,8 +706,6 @@ func (s *Server) Shutdown() {
 	s.StopPushNotificationsHubWorkers()
 	s.htmlTemplateWatcher.Close()
 
-	s.WaitForGoroutines()
-
 	s.platform.StopSearchEngine()
 
 	s.Audit.Shutdown()
@@ -814,11 +812,6 @@ func (s *Server) GoBuffered(f func()) {
 	s.platform.GoBuffered(f)
 }
 
-// WaitForGoroutines blocks until all goroutines created by App.Go exit.
-func (s *Server) WaitForGoroutines() {
-	s.platform.WaitForGoroutines()
-}
-
 var corsAllowedMethods = []string{
 	"POST",
 	"GET",