Discord bot speech synthesis

bot.js

const Discord = require('discord.js');
const client = new Discord.Client();
const textToSpeech = require('@google-cloud/text-to-speech');
const fs = require('fs');
const util = require('util');
const tts = new textToSpeech.TextToSpeechClient();

const writeFile = util.promisify(fs.writeFile);
client.on('message', async message => {
    if (!message.guild) return;

    if (message.content.startsWith('.say ')) {
        const text = message.content.replace('.say ', '')
        // Only try to join the sender's voice channel if they are in one themselves
        if (message.member.voice.channel) {
            const connection = await message.member.voice.channel.join();

            const request = {
                input: { text },
                voice: { languageCode: 'en-US', ssmlGender: 'NEUTRAL' },
                audioConfig: { audioEncoding: 'MP3' },
            };

            const [response] = await tts.synthesizeSpeech(request);
            await writeFile('output.mp3', response.audioContent, 'binary');
            connection.play('output.mp3');
        } else {
            message.reply('You need to join a voice channel first!');
        }
    }
});

client.login('secret token from discord here');