Flutter workmanager not working in ios background

I have downloaded workmanager repository on Github. then I add some code in the callback dispatcher. I have included the code below. Then I debug using Xcode.

After pressing the Background Fetch button (in Xcode), the app went minimize & starts warkmanager by showing a local notification. but when I close my app (terminate, remove from recent), not running in the background.

when the app is minimized, the app is working fine. but not working in the background.

I have tested with the release build.

what should I do right now?

This code I added inside the callback dispatcher

for (int i = 0; i < 1000; i++) {
      await Future.delayed(const Duration(seconds: 5));
      AwesomeNotifications().createNotification(
          content: NotificationContent(
              id: 10,
              channelKey: 'basic_channel',
              title: i.toString(),
              body: 'Workmanager '));
      print("background $i");
    }
    await Future.delayed(const Duration(minutes: 15));

I have initialized the notification package before this code.