ios – UIKit robotically change to a different VC after launch display screen seem

I am attempting to robotically change from lauch display screen to residence display screen after 3 sec.
That is code in entry level view controller

        override func viewDidAppear(_ animated: Bool) {
                DispatchQueue.foremost.asyncAfter(deadline: .now() + .seconds(3)) {
                     let mainStoryboard: UIStoryboard = UIStoryboard(identify: "Principal", bundle: nil)
                     let viewController = enter code heremainStoryboard.instantiateViewController(withIdentifier: "GenresNC") 
                     UIApplication.shared.home windows.first?.rootViewController = display screen
                     self.view.window?.makeKeyAndVisible()
                }
            }
 

It brakes at line with mainStoryboard…
Thread 1: EXC_BAD_ACCESS (code=2, deal with=0x16f5c7de8)

Can any person assist ?