How to use the teslajs.refreshToken function in teslajs

function auth() {
	log("Decrypting refresh token");
	let refreshToken = McCrypto.decrypt(process.env.ENCRYPTION_KEY, new Buffer(Config.tesla.encryptedToken, 'base64'));

	log("Obtaining new bearer token...");
	Tesla.refreshToken(refreshToken, (err, res) => {
		if (err) {
			throw err;
		}

		let body = JSON.parse(res.body);

		if (!body || !body.access_token || !body.refresh_token || !body.expires_in) {
			throw new Error("Got malformed response");
		}

		log("Got new refresh token " + body.refresh_token.substring(0, 6) + "...");
		g_BearerToken = body.access_token;
		Config.tesla.encryptedToken = McCrypto.encrypt(McCrypto.Cipher.AES256CTRWithHMAC, process.env.ENCRYPTION_KEY, body.refresh_token).toString('base64');
		FS.writeFileSync(__dirname + '/config.json', JSON.stringify(Config, undefined, "\t"));

		g_BearerTokenExpiresTime = Date.now() + (1000 * (body.expires_in - (60 * 60)));