DNS Lookup resolve failed in @swoole-src/library/core/Database/MysqliPool.php on line 40

[siddjain]

we are new to Swoole. This is our code:

Co\run(function() {
    go(function () {
        $pool = new MysqliPool(
        (new MysqliConfig())
            ->withHost('hackathon-mysql-8')
            ->withPort(3306)
            // ->withUnixSocket('/tmp/mysql.sock')
            ->withDbName('myDB')
            ->withCharset('utf8mb4')
            ->withUsername('root')
            ->withPassword('XXX')
        );
        $conn = $pool->get();
        echo "got MySQL connection";
    });    
});

and it results in this runtime error:

Warning: mysqli::real_connect(): (HY000/2002): DNS Lookup resolve failed in @swoole-src/library/core/Database/MysqliPool.php on line 40

Fatal error: Uncaught Swoole\Database\MysqliException: DNS Lookup resolve failed in @swoole-src/library/core/Database/MysqliPool.php:43
Stack trace:
#0 @swoole-src/library/core/Database/MysqliProxy.php(46): Swoole\Database\MysqliPool->Swoole\Database\{closure}()
#1 @swoole-src/library/core/ConnectionPool.php(89): Swoole\Database\MysqliProxy->__construct(Object(Closure))
#2 @swoole-src/library/core/ConnectionPool.php(58): Swoole\ConnectionPool->make()
#3 /app/server.php(27): Swoole\ConnectionPool->get()
#4 {main}
  thrown in @swoole-src/library/core/Database/MysqliPool.php on line 43
terminate called after throwing an instance of 'std::bad_function_call'
  what():  bad_function_call

our container is joined to the default bridge network. How can we fix this error?

We are using 4.5.9 of Swoole and php:8.0-cli Docker image.