nethttp/utils.go
func GetMaxAge(r *http.Request) entry.LifeChanger {
	return func() time.Duration {
		cacheControlHeader := r.Header.Get("Cache-Control")
		// headerCacheDur returns the seconds
		headerCacheDur := entry.ParseMaxAge(cacheControlHeader)
		return time.Duration(headerCacheDur) * time.Second
	}
}
func GetMaxAge(r *http.Request) entry.LifeChanger {
	return func() time.Duration {
		cacheControlHeader := r.Header.Get("Cache-Control")
		// headerCacheDur returns the seconds
		headerCacheDur := entry.ParseMaxAge(cacheControlHeader)
		return time.Duration(headerCacheDur) * time.Second
	}
}
// GetMaxAge parses the "Cache-Control" header
// and returns a LifeChanger which can be passed
// to the response's Reset