code: func (v *validatorRule) Valid(w http.ResponseWriter, r *http.Request) bool {
  	// check if it's a valid response, if it's not then just return.
  	for _, valid := range v.postValidators {
  		if !valid(w, r) {
  			return false
  		}
  	}
  	return true
  }
docs: // Valid returns true if incoming request and post-response from the original handler
  // is valid to be store to the cache, if not(false) then the consumer should just exit
  // otherwise(true) the consumer should store the cached response