code: func Basic(realm string, f func(user, passwd string) bool) goproxy.ReqHandler {
  	return goproxy.FuncReqHandler(func(req *http.Request, ctx *goproxy.ProxyCtx) (*http.Request, *http.Response) {
  		if !auth(req, f) {
  			return nil, BasicUnauthorized(req, realm)
  		}
  		return req, nil
  	})
  }
docs: // Basic returns a basic HTTP authentication handler for requests
  //
  // You probably want to use auth.ProxyBasic(proxy) to enable authentication for all proxy activities