err      error
	buf      [2]byte
	checkEnd bool  // whether need to check for \r\n chunk footer
	excess   int64 // "excessive" chunk overhead, for malicious sender detection
}

func (cr *chunkedReader) beginChunk() {
	// chunk-size CRLF
	var line []byte
	line, cr.err = readChunkLine(cr.r)
	if cr.err != nil {
		return
	}
	cr.excess += int64(len(line)) + 2 // header, plus \r\n after the chunk data