isHTTP := scheme == "http" || scheme == "https"
	if isHTTP {
		// Validate the outgoing headers.
		if err := validateHeaders(req.Header); err != "" {
			req.closeBody()
			return nil, fmt.Errorf("net/http: invalid header %s", err)
		}

		// Validate the outgoing trailers too.
		if err := validateHeaders(req.Trailer); err != "" {
			req.closeBody()
			return nil, fmt.Errorf("net/http: invalid trailer %s", err)
		}
	}