解决方法有2个：
1、升级swoole的openssl版本；
2、代码中加入GuzzleHttp请求options参数中加上：‘handler’ => HandlerStack::create(new CoroutineHandler()),

<?php
use GuzzleHttp\Client;
use Hyperf\Guzzle\CoroutineHandler;
use GuzzleHttp\HandlerStack;

$client = new Client([
    'base_uri' => 'http://127.0.0.1:8080',
    'handler' => HandlerStack::create(new CoroutineHandler()),
    'timeout' => 5,
    'swoole' => [
        'timeout' => 10,
        'socket_buffer_size' => 1024 * 1024 * 2,
    ],
]);

$response = $client->get('/');

来源：https://blog.csdn.net/weixin_45275983/article/details/128018554