code: func (mc MongoClient) getReading(q bson.M) (models.Reading, error) {
  	s := mc.getSessionCopy()
  	defer s.Close()
  
  	var res models.Reading
  	if err := s.DB(mc.database.Name).C(db.ReadingsCollection).Find(q).One(&res); err != nil {
  		return models.Reading{}, errorMap(err)
  	}
  	return res, nil
  }
docs: // Get a reading from the database with the passed query