garbagecollection.dart

import 'dart:async';

class A {
  var ctrl = StreamController();
  var cc = 0;
  
  run() {
    ctrl.stream.forEach((ev) {
    print(ev ?? 0);
  });
  
  Timer.periodic(Duration(seconds: 1), (tm) {
    ctrl?.add(cc++);
  });
  }
}

void main() async {
  var a = A();
  
  a.run();
  
  Timer(Duration(seconds: 5), () {
    a = null;
  });
}