How to use the ibm-watson/auth.IamTokenManager function in ibm-watson

* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

const express = require('express');

const app = express();
const { IamTokenManager } = require('ibm-watson/auth');

// Bootstrap application settings
require('./config/express')(app);

const serviceUrl = process.env.SPEECH_TO_TEXT_URL;

const tokenManager = new IamTokenManager({
  apikey: process.env.SPEECH_TO_TEXT_IAM_APIKEY || '',
});


app.get('/', (req, res) => res.render('index'));

// Get credentials using your credentials
app.get('/api/v1/credentials', async (req, res, next) => {
  try {
    const accessToken = await tokenManager.getToken();
    res.json({
      accessToken,
      serviceUrl,
    });
  } catch (err) {
    next(err);