close method
cancels stream subscription and closes relay transport
Implementation
Future<void> close() async {
if (_streamSubscription != null) {
await _streamSubscription!.cancel();
}
if (relayTransport != null) {
await relayTransport!.close().timeout(const Duration(seconds: 3),
onTimeout: () {
Logger.log.w("timeout while trying to close socket $url");
});
}
}