That’s indeed true, but it wasn’t a constraint so I thought it may be of interest to post it :D should have added a note regarding that though, but I can no longer edit.
Go's net/http is essentially the only used Go HTTP(S) server. It is often wrapped with other libs to add things like request routing, but it is always used as the actual HTTP implementation. Not sure why you're saying its purpose is "hello world".
The Java one is not usable in anything beyond hello world, and is explicitly not intended to be.
As someone maintaining a pretty large networking industry proprietary app based entirely on net/http in terms of any kind of HTTP communication, I feel like I can easily tell you are wildly exaggerating. Admin consoles and enterprise connectors are entirely irrelevant to many uses of an HTTP server. Hell, even Kubernetes' API server is built using net/http.
There is frequently a reverse proxy in front of all web services. It’s got nothing to do with the quality of the implementation behind the curtains. And “the actual load” is by definition managed by the endpoint not the router.
I mean it would be trivial to implement that reverse proxy in Go. And I do mean trivial; Go also includes a reverse proxy utility, so you can implement something basic in about 5 LOC.
At this point it’s hard to believe you’re being genuine.
Kubernetes API server is not dependent on Apache, NGINX, HA Proxy, IIS, ... taking care of the actual load, since it's not getting any significant amount of traffic. In general API servers have much bigger scaling problems with actually executing the API calls rather than handling requests at scale. Having an NGINX or something similar to serve some static content and also reverse proxy to a Go server is sometimes nice if you're also serving a large UI app, but in that case NGINX is very much doing trivial work, and Go net/http is handling the real work.