Function fixTrailer

transfer.go:702–741

Parse the trailer header.

(header http.Header, chunked bool)

// Parse the trailer header.
func fixTrailer(header http.Header, chunked bool) (http.Header, error) {
	vv, ok := header["Trailer"]
	if !ok {
		return nil, nil
	}
	if !chunked {
		// Trailer and no chunking:
		// this is an invalid use case for trailer header.
		// Nevertheless, no error will be returned and we
		// let users decide if this is a valid HTTP message.
		// The Trailer header will be kept in Response.Header
		// but not populate Response.Trailer.
		// See issue #27197.
		return nil, nil
	}
	header.Del("Trailer")

	trailer := make(http.Header)
	var err error
	for _, v := range vv {
		foreachHeaderElement(v, func(key string) {
			key = http.CanonicalHeaderKey(key)
			switch key {
			case "Transfer-Encoding", "Trailer", "Content-Length":
				if err == nil {
					err = badStringError("bad trailer key", key)
					return
				}
			}
			trailer[key] = nil
		})
	}
	if err != nil {
		return nil, err
	}
	if len(trailer) == 0 {
		return nil, nil
	}
	return trailer, nil
}

// body turns a textprotoReader into a ReadCloser.
// Close ensures that the body has been fully read