waitgroup

示例代码：

go(function (){
    $ret = [];
    $wait = new \EasySwoole\Component\WaitGroup();
    $wait->add();
    go(function ()use($wait,&$ret){
        \co::sleep(0.1);
        $ret[] = time();
        $wait->done();
    });
    $wait->add();
    go(function ()use($wait,&$ret){
        \co::sleep(2);
        $ret[] = time();
        $wait->done();
    });
    $wait->wait();
    var_dump($ret);
});