Can't make a bot speak using Discord's websocket

Question

This is my code:

const WebSocket = require('ws');
const dgram = require('dgram');
const fs = require('fs');

function start(token, guild, endpoint, id, session) {
    console.log(token, guild, endpoint, id, session);

    console.log('Connecting to voice gateway...');
    // Play audio.mp3
    const audio = fs.readFileSync('audio.mp3');
    const ws = new WebSocket("wss:" + endpoint);
    ws.on('open', () => {
        console.log('Connected to voice gateway');
        ws.send(JSON.stringify({
            op: 0,
            d: {
                server_id: guild,
                user_id: id,
                session_id: session,
                token: token
            }
        }));
    })
    ws.on('message', (data) => {
        data = JSON.parse(data);
        console.log(data);
        if (data.op === 2) {
            console.log('Received voice gateway data');
            const udp = dgram.createSocket('udp4');
            udp.send(audio, 0, audio.length, data.d.port, data.d.ip);
            udp.on('message', (data) => {
                console.log(data);
            });

            // Send heartbeat
            setInterval(() => {
                ws.send(JSON.stringify({
                    op: 3,
                    d: Date.now()
                }));
            }
            , data.d.heartbeat_interval);

            
        }
    })

    
 
            
}
    


module.exports = { start };

For some reason, nothing happens when I start the function after my bot joins the voice, I have an already made audio.mp3 file ready, I just can't find a good way to stream it to the websocket.

https://discord.com/developers/docs/topics/voice-connections