override func viewDidLoad() {
    super.viewDidLoad()

    NotificationCenter.default.addObserver(self, selector: #selector(GameViewController.doaSegue), name: NSNotification.Name(rawValue: "doaSegue"), object: nil)

//I kept out all of the code for setting up the scene
}


@objc func doaSegue(){

    performSegue(withIdentifier: "show", sender: self) //The error occurs on this line
    self.view.removeFromSuperview()
    self.view = nil

}

let Action1 = SKAction.fadeAlpha(to: 0.75, duration: 5)

        let Action2 = SKAction.run {

            print("segue")
            NotificationCenter.default.post(name: NSNotification.Name(rawValue: "doaSegue"), object: nil)

        }

        shape.run(SKAction.sequence([Action1, Action2]))

// let Action2 = SKAction.run {

            print("segue")
            NotificationCenter.default.post(name: NSNotification.Name(rawValue: "doaSegue"), object: nil)

      //  }

       // shape.run(SKAction.sequence([Action1, Action2]))