code: func (ch *Chunk) Jump(bytesAhead int) error {
  	var err error
  	var n int64
  	if bytesAhead > 0 {
  		n, err = io.CopyN(ioutil.Discard, ch.R, int64(bytesAhead))
  		ch.Pos += int(n)
  	}
  	return err
  }
docs: // Jump jumps ahead in the chunk