code: func (c *MockClient) Flush(expiration uint32) Response {
  	c.mutex.Lock()
  	defer c.mutex.Unlock()
  
  	// TODO(patrick): Use expiration argument
  	c.data = make(map[string]*Item)
  	return NewResponse(StatusNoError)
  }
docs: // This invalidates all existing cache items after expiration number of
  // seconds.