UINavigationController+PushCompletion.swift

extension UINavigationController {
    
    func pushViewController(_ viewController: UIViewController, animated: Bool, completionHandler: (() -> Void)?) {
        pushViewController(viewController, animated: animated)
        viewController.transitionCoordinator.animate(alongsideTransition: nil) { _ in
          completionHandler?()
        }
    }
}