First gcloud use for node.js

creating_users.js

var gcloud = require('gcloud')({
  projectId: 'testing-project',
  apiEndpoint: 'http://localhost:8080'
});

function createUser(userData){
  return new Promise((resolve, reject) => {
    const key = datastore.key(['Users', userData.dni]);
    datastore.save({ key: key, data: userData }, err => {
      if (!err) {
        resolve();
      } else {
        reject(err);
      }
    });
  });
}