import 'dart:math';

var random = Random.secure();

Future<int> rand()  {
  return Future.delayed(new Duration(seconds: 1), () { return random.nextInt(200); });
}

Future<int> get() async {
  print("beginning to save");
  int n = await rand();
  if (n < 100) {
    throw "unlucky";
  }
  return n - 100;
}

Future<int> persevere() async {
  while(true) {
   try {
    return await get();
   } catch(e) {
     print('error ${e}, retrying');
   }
  }
}

void main() {
  persevere().then((int a) {
    print('ok ${a}');
  });
  print("after then");
}