why is my Node/Express application leaking MySQL connections?

I just don’t understand why the below code opens a new connection/pool for every request it gets. As a result, this code generates hundreds of open connections and eventually crashes within an hour or less.

Added the error message at the bottom.

db.js

function connection() {
    try {
        const mysql = require('mysql2');
        const config = require('../config');

        const pool = mysql.createPool(config.db);
        const promisePool = pool.promise();

        return promisePool;
    } catch (error) {
        return console.log(`Could not connect - ${error}`);
    }
}

const pool = connection();

module.exports = {
    connection: async () => pool.getConnection(),
    execute: (...params) => pool.execute(...params)
};

config.js

const config = {
    db: {
        host: process.env.DB_HOST,
        port: process.env.DB_PORT,
        user: process.env.DB_USER,
        password: process.env.DB_PASSWORD,
        database: process.env.DB_NAME,
        connectionLimit: 10,
        waitForConnections: true,
        queueLimit: 0
    },
    listPerPage: 10,
};

module.exports = config;

And now the file where I query the database:

const db = require('./db');

async function getByName(name) {
    const sql = `SELECT name, pubkey FROM name WHERE name="${name}"`;

    const [result] = await db.execute(sql);

    if (result && result.length == 1) {
        var resp = JSON.parse(`{
            "names": {
                "${result[0].name}": "${result[0].pubkey}"
            }
        }`);

        return resp;
    } else {
        return {};
    }
}

Thanks for your help!

======= Update 1 =======

Full code can be found here:
https://github.com/sebastiansieber/nostr-nip05-verification

(Don’t worry it’s a small repository, you’ll find above files easily)

======= Update 2 =======

This is the error message I receive when the application exits due to too many connections

Error: Too many connections
    at Packet.asError (/usr/src/app/node_modules/mysql2/lib/packets/packet.js:728:17)
    at ClientHandshake.execute (/usr/src/app/node_modules/mysql2/lib/commands/command.js:29:26)
    at PoolConnection.handlePacket (/usr/src/app/node_modules/mysql2/lib/connection.js:487:32)
    at PacketParser.onPacket (/usr/src/app/node_modules/mysql2/lib/connection.js:94:12)
    at PacketParser.executeStart (/usr/src/app/node_modules/mysql2/lib/packet_parser.js:75:16)
    at Socket.<anonymous> (/usr/src/app/node_modules/mysql2/lib/connection.js:101:25)
    at Socket.emit (node:events:394:28)
    at addChunk (node:internal/streams/readable:312:12)
    at readableAddChunk (node:internal/streams/readable:287:9)
    at Socket.Readable.push (node:internal/streams/readable:226:10) {
  code: 'ER_CON_COUNT_ERROR',
  errno: 1040,
  sqlState: '',
  sqlMessage: 'Too many connections',

======= Update 3 =======

As requested please see how the process list looks like: