code: func (mc MongoClient) getReadingsLimit(q bson.M, limit int) ([]models.Reading, error) {
  	s := mc.getSessionCopy()
  	defer s.Close()
  
  	// Check if limit is 0
  	if limit == 0 {
  		return []models.Reading{}, nil
  	}
  
  	var readings []models.Reading
  	if err := s.DB(mc.database.Name).C(db.ReadingsCollection).Find(q).Sort("-modified").Limit(limit).All(&readings); err != nil {
  		return []models.Reading{}, errorMap(err)
  	}
  	return readings, nil
  }
docs: // Return a list of readings that match.
  // Sort the list before applying the limit so we can return the most recent readings