// async/await - check out a client
;(async () => {
  const client = await pool.connect()
  try {
    const res = await client.query('SELECT * FROM users WHERE id = $1', [1])
    console.log(res.rows[0])
  } finally {
    // Make sure to release the client before any error handling,
    // just in case the error handling itself throws an error.
    client.release()
  }
})().catch(err => console.log(err.stack))