public function updateToken()
 {
     $accessToken = new AccessToken($this->_appId, $this->_secret);
     $token = $accessToken->getToken();
     $cache = new Cache($this->_appId);
     $this->show($token);
     $cache->forget('overtrue.wechat.access_token');
     $this->show($accessToken->getToken());
 }