Node.js Error: personFields mask is required. Please specify one or more valid paths when trying to get google contacts

Question

I am working on node.js, googleapi and oauth2. I am enabling gmail api and google people api. using gmail api methods, getting the profile info and its working fine where as people api methods are not working. I am getting the following error when i am trying to get google contacts using people.people.get():

Error: personFields mask is required. Please specify one or more valid paths.

Here is my code:

var people = google.people('v1');
people.people.get({
auth: auth,
userId: 'me',
resourceName: 'people/me',
personFields: 'names,emailAddresses',
}, function(err, res) {
  if (err) {
      console.log(err);
  } else {
  console.log(res);
  }
});

I am using personFields but still same error. please help me out.