code: func (m *MongoCache) Get(key string) (interface{}, error) {
  	data, err := m.get(key)
  	if err == mgo.ErrNotFound {
  		return nil, ErrNotFound
  	}
  
  	if err != nil {
  		return nil, err
  	}
  
  	return data.Value, nil
  }
docs: // Get returns a value of a given key if it exists