I want something like Cloudflare’s server push mechanism
Cloudflare supports HTTP/2 Server Push via the Link header. To make use of Server Push, most applications will need to change their code to include a Link header with any requests that have pushable assets.
For example, if you have a web page called page.html that requires /css/style.css, you need to add the following header to page.html:
Link: </css/style.css>; rel=preload;
This tells our edge network to begin pushing /css/style.css every time a visitor asks for page.html. If style.css is already in the local browser cache, the browser will ignore the push and cancel the download. Otherwise, when it discovers /css/style.css while rendering the HTML, the browser will use the pushed asset instead of going back to the server. This removes an unnecessary round-trip that would have occurred without Server Push.