Fix sleep

src/Timer.php

@@ -22,6 +22,7 @@ use Throwable;
 use Workerman\Events\EventInterface;
 use Workerman\Events\Revolt;
 use Workerman\Events\Swoole;
+use Workerman\Events\Swow;
 use function function_exists;
 use function is_callable;
 use function pcntl_alarm;