我尝试使用基于this教程的Node.js连接到我的MariaDB数据库：

const mariadb = require('mariadb');
const pool = mariadb.createPool({
     host: 'myhost.com',
     user:'root', 
     password: 'password',
     database: 'db_p',
     connectionLimit: 2
});

async function asyncFunction() {
  let conn;
  try {
    console.log('establishing connection')
    conn = await pool.getConnection();
    console.log('established')
    const rows = await conn.query("SHOW TABLES");
    console.log(rows);

  } catch (err) {
    console.log(err)
      throw err;
  } finally {
      if (conn) return conn.end();
  }
}

但我得到的只是这个错误：

establishing connection
{ Error: retrieve connection from pool timeout
    at Object.module.exports.createError (/Users/jan/Developer/microservice/node_modules/mariadb/lib/misc/errors.js:55:10)
    at rejectTimeout (/Users/jan/Developer/microservice/node_modules/mariadb/lib/pool.js:267:16)
    at Timeout.rejectAndResetTimeout [as _onTimeout] (/Users/jan/Developer/microservice/node_modules/mariadb/lib/pool.js:287:5)
    at ontimeout (timers.js:486:15)
    at tryOnTimeout (timers.js:317:5)
    at Timer.listOnTimeout (timers.js:277:5)
  fatal: false,
  errno: 45028,
  sqlState: 'HY000',
  code: 'ER_GET_CONNECTION_TIMEOUT' }
(node:76515) UnhandledPromiseRejectionWarning: Error: retrieve connection from pool timeout
    at Object.module.exports.createError (/Users/jan/Developer/microservice/node_modules/mariadb/lib/misc/errors.js:55:10)
    at rejectTimeout (/Users/jan/Developer/microservice/node_modules/mariadb/lib/pool.js:267:16)
    at Timeout.rejectAndResetTimeout [as _onTimeout] (/Users/jan/Developer/microservice/node_modules/mariadb/lib/pool.js:287:5)
    at ontimeout (timers.js:486:15)
    at tryOnTimeout (timers.js:317:5)
    at Timer.listOnTimeout (timers.js:277:5)
(node:76515) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This errororiginated either by throwing inside of an async function without a catch block, or byrejecting a promise which was not handled with .catch(). (rejection id: 2)
(node:76515) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

我在过去两年里用JS编程，但我是Node.js的新手，我认为它应该开箱即用。有人知道吗？