I am developing a react web application that fetches data from a server. A NodeJS API script running on the server is used to send queries to a MySQL database and retrieve the data. I am creating a pooled connection to the database using the following program which is called by the API :

db_connect.js:

const mysql = require('mysql2/promise'); 
const db_connect = mysql.createPool({
    host     : 'host',
    user     : 'username',
    password : 'password',
    database : 'database',
    port : 1234
  });
  


module.exports = db_connect;

api.js

const express = require('express');
const app = express();
app.use(express.json()); 
const db_connect = require('./db_connect');
app.post('/api',(req,res,next)=>{
    const query = "SELECT col1 FROM tbl WHERE col2=?"; 
    const value = req.body.data;
    const data = [value];
    db_connect.query(query,data)
    .then((result)=> {
        res.json({response: result});
     });
});

Every time I run the API program a new connection to the MySQL database is added. I am expecting the program to close the condition as soon as the API completes executing. But it just keeps adding a new connection every time it is called. How can I close the connection?