code: func UrlHasPrefix(prefix string) ReqConditionFunc {
  	return func(req *http.Request, ctx *ProxyCtx) bool {
  		return strings.HasPrefix(req.URL.Path, prefix) ||
  			strings.HasPrefix(req.URL.Host+req.URL.Path, prefix) ||
  			strings.HasPrefix(req.URL.Scheme+req.URL.Host+req.URL.Path, prefix)
  	}
  }
docs: // UrlHasPrefix returns a ReqCondition checking wether the destination URL the proxy client has requested
  // has the given prefix, with or without the host.
  // For example UrlHasPrefix("host/x") will match requests of the form 'GET host/x', and will match
  // requests to url 'http://host/x'