GatewayWorker的Even.php使用mysql连接 Class 'Workerman\MySQL\Connection' not found

use \GatewayWorker\Lib\Gateway;
use \GatewayWorker\Lib\Db;

public static $mysql = null;
public static function onWorkerStart($worker)
{
     self::$mysql = new Workerman\MySQL\Connection('127.0.0.1', '3306', 'root', 'root', 'workerman');
}