Creating a custom stream

main.dart

import 'dart:async';

class DataCreator {
  final _controller = StreamController<String>();
  int _count = 1;
  DataCreator() {
    Timer.periodic(Duration(seconds: 1), (callBack) {
      _controller.sink.add('String $_count');
      _count++;
    });
  }
  Stream<String> get stream => _controller.stream;

  void dispose() {
    _controller.close();
  }
}

main() {
  var subscription =
      DataCreator().stream.listen((data) => print(data));
  
  Timer(Duration(seconds:20),(){
    subscription.cancel();
  });
  
}