refresh method

Future<NetworkType> refresh()

主动刷新一次（App 从后台回前台时建议调用）

Implementation

Future<NetworkType> refresh() async {
  try {
    final results = await _connectivity.checkConnectivity();
    _apply(results, notifyCallbacks: true);
  } catch (e) {
    GoChatLogger.e('ConnectivityMonitor refresh failed', e);
  }
  return _type;
}