Keeping the Flutter connection open 
in debug mode when the phone screen locks.

Creating a FlutterAppDelegate subclass

Creating a subclass of the the FlutterAppDelegate in UIKit apps was shown 
in the Start a FlutterEngine and FlutterViewController section. 
In a SwiftUI app, you can create a subclass of the 
FlutterAppDelegate that conforms to the ObservableObject protocol as follows:

import

SwiftUI

import

Flutter

import

FlutterPluginRegistrant

class

AppDelegate

FlutterAppDelegate

ObservableObject

let

flutterEngine

FlutterEngine

name

"my flutter engine"

override

func

application

application

UIApplication