code: func (s *Store) Restore(r io.ReadCloser) error {
  	s.mu.Lock()
  	defer s.mu.Unlock()
  
  	data := &raftData{}
  	if err := json.NewDecoder(r).Decode(data); err != nil {
  		return err
  	}
  	s.data = data
  	return nil
  }
docs: // Restore implements raft.FSM.