code: func (r *ByteSliceReader) Read(buf []byte) (int, error) {
  	count := copy(buf, *r)
  	*r = (*r)[count:]
  	if len(*r) == 0 {
  		*r = nil
  	}
  	if count < len(buf) {
  		return count, io.EOF
  	}
  	return count, nil
  }
docs: // Read implements io.Reader.