@BenderBoy has a good point there. I am not familiar with Go. But on your endpoints you should have access to request and response. Check the "HX-Request" header in the request.
if (headers['hx-request'] == true) {
return partial_page;
} else {
return full_page;
}
Depends on your UI framework. But with templating your partial_page would be included in your full_page.