Resolve "Application that allows to access events through websocket"

Description

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

Closes #301

applications/ws-events/app.go

@@ -22,9 +22,10 @@ type Application struct {
 }
 
 // Run runs the application.
-func (a *Application) Run() {
+func (a *Application) Run() error {
 	signal.Notify(a.stopChannel, os.Interrupt, syscall.SIGTERM)
 
+	// subscribe to Add,Delete and Update event types.
 	a.eventService.SubscribeToEventType([]event.TypeToCallbackTuple{
 		{Type: event.Add, Callback: a.callback},
 		{Type: event.Delete, Callback: a.callback},
@@ -43,16 +44,18 @@ func (a *Application) Run() {
 
 	err := svr.Start()
 	if err != nil {
-		fmt.Printf("Server start failed: %v\n", err)
-		return
+		return fmt.Errorf("Server start failed: %w\n", err)
 	}
 
 	<-a.stopChannel
 	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
 	defer cancel()
-	svr.Shutdown(ctx)
+	return svr.Shutdown(ctx)
 }
 
+// callback handles an incoming event from the event system. The event is
+// turned into JSON encoding and published to all websocket clients through the
+// ClientManager.
 func (a *Application) callback(event *event.Event) {
 	b, err := json.Marshal(event)
 	if err != nil {