HowtogettransfertimeforPoolrequestsinguzzle6?我想获取每个请求的传输时间。如何将on_stats选项用于异步请求？http://docs.guzzlephp.org/en/latest/request-options.html#on-stats我的代码：1234567891011121314useGuzzleHttp\\{Pool,Client};useGuzzleHttp\\Psr7\\{Request,Response};$httpClient=newClient();foreach($itemsas$request){  $requests[]