type eofReader struct {
	data     []byte // deliver from Read without EOF
	dataEOF  []byte // then deliver from Read with EOF on last chunk
	lenAtEOF int
}

func (r *eofReader) Read(b []byte) (n int, err error) {
	if len(r.data) > 0 {
		n = copy(b, r.data)
		r.data = r.data[n:]
	} else {
		n = copy(b, r.dataEOF)
		r.dataEOF = r.dataEOF[n:]
		if len(r.dataEOF) == 0 {
			err = io.EOF
			if r.lenAtEOF == -1 {