code: func (b *ByteBuf) ReadRawBytes(n int) (int, []byte, error) {
  	if n > b.Readable() {
  		return 0, nil, nil
  	}
  
  	return n, b.buf[b.readerIndex : b.readerIndex+n], nil
  }
docs: // ReadRawBytes read bytes from buf without mem copy
  // Note. If used complete, you must call b.Skip(n) to reset reader index