if !usingProxy {
			host = ""
		} else {
			return errors.New("http: invalid Host header")
		}
	}

	// According to RFC 6874, an HTTP client, proxy, or other
	// intermediary must remove any IPv6 zone identifier attached
	// to an outgoing URI.
	host = removeZone(host)

	ruri := r.URL.RequestURI()
	if usingProxy && r.URL.Scheme != "" && r.URL.Opaque == "" {