连接到数据库，nodeJS / mySQL时无法执行查询

Question

连接到数据库时查询似乎无法正常工作，并且json字符串似乎为空，我收到以下错误 {“代码”：“ PROTOCOL_ENQUEUE_AFTER_FATAL_ERROR”，“致命”：false} < / p>

const express = require('express');
const cors = require('cors');
const mysql = require('mysql');
const app = express();


const selectAllClients = "SELECT * from clients";

const connection = mysql.createConnection({
host: 'localhost',
user: 'root',
password: 'root',
database: 'dashboard',
multipleStatements: true
});

console.log(connection);
app.use(cors());

app.get('/clients', (req, res) =>{

connection.query(selectAllClients, (err, results) => {
    if(err){
        return res.send(err);
    }
    else
    {
        return res.json({
            data: results
        })
    }

});
});

app.listen(4000, () => {
console.log('Server listening on port 4000')
});