Method readTrailer

transfer.go:840–880

()

var errTrailerEOF = errors.New("http: unexpected EOF reading trailer")

func (b *body) readTrailer() error {
	// The common case, since nobody uses trailers.
	buf, err := b.r.Peek(2)
	if bytes.Equal(buf, singleCRLF) {
		b.r.Discard(2)
		return nil
	}
	if len(buf) < 2 {
		return errTrailerEOF
	}
	if err != nil {
		return err
	}

	// Make sure there's a header terminator coming up, to prevent
	// a DoS with an unbounded size Trailer. It's not easy to
	// slip in a LimitReader here, as textproto.NewReader requires
	// a concrete *bufio.textprotoReader. Also, we can't get all the way
	// back up to our conn's LimitedReader that *might* be backing
	// this bufio.textprotoReader. Instead, a hack: we iteratively Peek up
	// to the bufio.textprotoReader's max size, looking for a double CRLF.
	// This limits the trailer to the underlying buffer size, typically 4kB.
	if !seeUpcomingDoubleCRLF(b.r) {
		return errors.New("http: suspiciously long trailer after chunked body")
	}

	hdr, err := textproto.NewReader(b.r).ReadMIMEHeader()
	if err != nil {
		if err == io.EOF {
			return errTrailerEOF
		}
		return err
	}
	switch rr := b.hdr.(type) {
	case *http.Request:
		mergeSetHeader(&rr.Trailer, http.Header(hdr))
	case *http.Response:
		mergeSetHeader(&rr.Trailer, http.Header(hdr))
	}
	return nil
}

func mergeSetHeader(dst *http.Header, src http.Header) {
	if *dst == nil {