title: self.navigationController?.pushViewController Not Working with Xcode 11.1
body: <p>I recently started a new project with the newest Xcode and now the function
  <code>self.navigationController?.pushViewController</code> to push a new controller is not working.</p>
  
  <p>I've looked at similar answers and checked my own old  projects where it is working, they mentioned the Navigation controller being <code>nil</code> but I thought I addressed that. </p>
  
  <p>I think it has to do with the new <code>SceneDelegate</code> file that is part of how views are managed.</p>
  
  <p>Here is the code of the regarding the first <code>VC</code> that pops up in the app in the <code>SceneDelegate</code> file.</p>
  
  <pre><code> let nav1 = UINavigationController()
          let mainView = MainViewController(nibName: nil, bundle: nil) //ViewController = Name of your controller
          nav1.viewControllers = [mainView]
          // Use a UIHostingController as window root view controller.
          if let windowScene = scene as? UIWindowScene {
              let window = UIWindow(windowScene: windowScene)
  //            window.rootViewController = UIHostingController(rootView: contentView)
              window.rootViewController = nav1
              self.window = window
              window.makeKeyAndVisible()
          }
  </code></pre>