See my example where a pure-rust postgres extension can start a background worker, listen on a port, and handle concurrent network requests, multiplexing them over a single backend calling a non-thread-safe internal postgres API.

That's possible because rust has no runtime to get in the way, it can use C structs natively and seamlessly, tokio offers the CurrentThread runtime (which doesn't spawn new threads), and a bunch of other details that need to be done right.

Try doing that in a pure-Go postgres extension.