我正在用node js和mysql连接lambdas到一个rds，第一次触发lambda函数时出现错误“process exited before completing request”，然后就可以正常工作了。
这是我的密码：

const mysql = require('mysql');

module.exports.selectAll = (event, context, callback) => {

    context.callbackWaitsForEmptyEventLoop = false;

    //Response
    let response = {
        status: 200,
        message: '',  
        data: [], 
    }

    //Body request
    const {user} = event

    const connection = mysql.createConnection({
        host: process.env.host_DB,
        user: process.env.user_DB,
        password: process.env.password_DB,
        database: process.env.database_DB

    });

    connection.open(); 

    connection.query(`call test_db.getAll('${user != undefined? user : 0}')`,
    function(err, results, fields) {
        if(err){
            console.log(err);
            response.status = 500; 
            response.message = err.message; 
            response.data = []; 
        }else{
            response.data = results[0]; 
            response.message = 'Success'; 
        }

        connection.end();
        callback(null, response);
    })
};

知道是什么引起的吗？