code: func (b *FastLogStore) Set(k, v []byte) error {
  	b.mu.Lock()
  	defer b.mu.Unlock()
  	if b.closed {
  		return ErrClosed
  	}
  	if b.persist {
  		b.buf = b.buf[:0]
  		b.buf = bufferSet(b.buf, k, v)
  		if err := b.writeBuf(); err != nil {
  			return err
  		}
  	}
  	b.kvm[string(k)] = v
  	return nil
  }
docs: // Set is used to set a key/value set outside of the raft log