docs: function getToken(code, token, oauth2Client, isCustomClient) {
      return new Promise((resolve, reject) => {
          if (isCustomClient) {
              getTokenCustom(code, oauth2Client).then((newToken) => {
                  oauth2Client.credentials = newToken;
                  storeToken(newToken);
                  resolve(oauth2Client);
                  return;
              }, (err) => {
                  reject(err);
                  return;
              });
          } else {
              getTokenDefault(code, token, oauth2Client).then((newToken) => {
                  oauth2Client.credentials = newToken;
                  storeToken(newToken);
                  resolve(oauth2Client);
                  return;
              }, (err) => {
                  reject(err);
                  return;
              });
          }
      });
  }