code: func (c *PCPClient) Start() error {
  	c.mutex.Lock()
  	defer c.mutex.Unlock()
  
  	l := c.Length()
  
  	writer, err := bytewriter.NewMemoryMappedWriter(c.loc, l)
  	if err != nil {
  		return errors.Wrap(err, "cannot create MemoryMappedBuffer in client")
  	}
  
  	c.writer = writer
  	c.start()
  	c.r.mapped = true
  	return nil
  }
docs: // Start dumps existing registry data