message: Feature/#586-Check-if-course-exists
  Change private to public for method goBack in NotFoundComponent.
diff: @@ -13,7 +13,7 @@ export class NotfoundComponent implements OnInit {
  ngOnInit() {
  }
  - private goBack() {
  + public goBack() {
  this.router.navigate(['/']);
  }
  }
  