Completer

main.dart

import 'dart:async';

void main() async{
  
  Future<int>testTimer(int i) {
    final completer=Completer<int>();
    Timer(Duration(seconds: 5), () {
      print("coucou from :$i");
      if (i != 3)
        completer.complete(i);
    });
    return completer.future;
  }
  
  for (int i = 0; i < 5; i++) {
    await testTimer(i);
    print("i: $i");
  }
  print("Fin");
  
}