How to use the ali-oss.STS function in ali-oss

app.use(async (ctx, next) => {
  lastReqTime = Date.now();
  if (ctx.path === '/api/oss-config') {
    ctx.body = {
      accessKeyId,
      accessKeySecret,
      bucket,
      region,
      endpoint,
    };
  }
  if (ctx.path === '/api/sts') {
    const sts = new STS({
      accessKeyId,
      accessKeySecret,
    });
    // 60 mins
    const expires = 60 * 60;
    const sessionName = 'foo';
    const stsToken = await sts.assumeRole(arn, undefined, expires, sessionName);
    ctx.body = {
      bucket,
      region,
      endpoint,
      stsToken,
    };
  }
  next();
});

app.get('/sts', (req, res) => {
  console.log(conf);
  let policy;
  if (conf.PolicyFile) {
    policy = fs.readFileSync(path.resolve(__dirname, conf.PolicyFile)).toString('utf-8');
  }

  const client = new STS({
    accessKeyId: conf.AccessKeyId,
    accessKeySecret: conf.AccessKeySecret
  });

  client.assumeRole(conf.RoleArn, policy, conf.TokenExpireTime).then((result) => {
    console.log(result);
    res.set('Access-Control-Allow-Origin', '*');
    res.set('Access-Control-Allow-METHOD', 'GET');
    res.json({
      AccessKeyId: result.credentials.AccessKeyId,
      AccessKeySecret: result.credentials.AccessKeySecret,
      SecurityToken: result.credentials.SecurityToken,
      Expiration: result.credentials.Expiration
    });
  }).catch((err) => {
    console.log(err);