読み上げをmp3にしようとした

前提・実現したいこと

Google Cloud Text-to-SpeechでNode.jsを使用し、テキストの読み上げ音声をmp3として取得しようとしているのですが、次のようなエラーが出ました。

発生している問題・エラーメッセージ

Error: Could not load the default credentials. Browse to https://cloud.google.com/docs/authentication/getting-started for more information.
    at GoogleAuth.getApplicationDefaultAsync (/home/runner/YuinaBOT-test/node_modules/google-auth-library/build/src/auth/googleauth.js:180:19)
    at processTicksAndRejections (node:internal/process/task_queues:96:5)
    at async GoogleAuth.getClient (/home/runner/YuinaBOT-test/node_modules/google-auth-library/build/src/auth/googleauth.js:558:17)
    at async GrpcClient._getCredentials (/home/runner/YuinaBOT-test/node_modules/google-gax/build/src/grpc.js:145:24)
    at async GrpcClient.createStub (/home/runner/YuinaBOT-test/node_modules/google-gax/build/src/grpc.js:308:23)

該当のソースコード

javascript
1const { Intents, Client } = require('discord.js');
2const { joinVoiceChannel, entersState, VoiceConnectionStatus, createAudioResource, StreamType, createAudioPlayer, AudioPlayerStatus, NoSubscriberBehavior, generateDependencyReport } = require("@discordjs/voice");
3const Discord = require('discord.js');
4const textToSpeech = require('@google-cloud/text-to-speech');
5const util = require('util');
6const options = {
7  intents: ['GUILDS', 'GUILD_MESSAGES', 'GUILD_MEMBERS', 'GUILD_VOICE_STATES'],
8};
9const client = new Discord.Client(options);
10const fs = require('fs');
11const { disconnect } = require('process');
12const { setFlagsFromString } = require('v8');
13/*
14その他の処理
15*/
16  } else if (msg.content.startsWith('--join')) {
17    const sclient = new textToSpeech.TextToSpeechClient();
18    const outputFile = 'test.mp3';
19    command = msg.content.split(' ');
20    const request = {
21      input: {text: command[1]},
22      voice: {languageCode: 'ja-JP', ssmlGender: 'FEMALE'},
23      audioConfig: {audioEncoding: 'MP3'},
24    };
25    const [response] = await sclient.synthesizeSpeech(request);
26    const writeFile = util.promisify(fs.writeFile);
27    await writeFile(outputFile, response.audioContent, 'binary');
28    return onCommandInteraction(msg);

補足情報（FW/ツールのバージョンなど）

"@discordjs/voice": "^0.6.0"
"@google-cloud/text-to-speech": "^3.3.1"
"discord.js": "^13.2.0"
"ffmpeg-static": "^4.4.0"
"har-validator": "^5.1.5"
"opus": "^0.0.0"
"request": "^2.88.2"
"util": "^0.12.4"
"uuid": "^8.3.2"

Node.js 16.10.0