dispose method

Implementation

@override
Future<void> dispose() async {
  _disposed = true;
  _stopInstabilitySimulation();
  for (final t in _timers) {
    t.cancel();
  }
  _timers.clear();
  await _stateController.close();
  await _messageController.close();
  await _errorController.close();
  _sentMessages.clear();
}