func GetHostname(req *http.Request) string {
	if req == nil {
		return ""
	}
	h, _, err := net.SplitHostPort(req.Host)
	if err != nil {
		return req.Host
	}
	return h
}
func GetHostname(req *http.Request) string {
	if req == nil {
		return ""
	}
	h, _, err := net.SplitHostPort(req.Host)
	if err != nil {
		return req.Host
	}
	return h
}
// GetHostname returns the hostname from request Host field.
// It returns empty string, if Host field contains invalid
// value (e.g. "localhost:::" with too many colons).