Flutter navigate to another view controller in iOS

self.appDelegate?.window?.rootViewController = nil
let navigationController = UINavigationController(rootViewController: self.controller!)
navigationController.isNavigationBarHidden = true
self.appDelegate?.window?.rootViewController = navigationController
self.appDelegate?.window?.makeKeyAndVisible()

let storyboard = UIStoryboard(name: "Meeting", bundle: nil)
if let container = storyboard.instantiateViewController(withIdentifier: "meeting") as? MeetingViewController {
    result("success")
    navigationController.pushViewController(container, animated: false)
}

// .... //
let container = storyboard.instantiateViewController(withIdentifier: "meeting") as! MeetingViewController
DispatchQueue.main.async {
    result("success")
    navigationController.pushViewController(container, animated: false)
}
// .... //