AngularJS: How to send auth token with $resource requests?

I want to send an auth token when requesting a resource from my API.

I did implement a service using $resource:

factory('Todo', ['$resource', function($resource) {
 return $resource('http://localhost:port/todos.json', {port:":3001"} , {
   query: {method: 'GET', isArray: true}
 });
}])

And I have a service that stores the auth token:

factory('TokenHandler', function() {
  var tokenHandler = {};
  var token = "none";

  tokenHandler.set = function( newToken ) {
    token = newToken;
  };
  tokenHandler.get = function() {
    return token;
  };

  return tokenHandler;
});

I would like to send the token from tokenHandler.get with every request send via the Todo service. I was able to send it by putting it into the call of a specific action. For example this works:

Todo.query( {access_token : tokenHandler.get()} );

But I would prefer to define the access_token as a parameter in the Todo service, as it has to be sent with every call. And to improve DRY. But everything in the factory is executed only once, so the access_token would have to be available before defining the factory and it cant change afterwards.

Is there a way to put a dynamically updated request parameter in the service?