If you know rust, the Godot rust bindings for GDExtension are also really good and let you use any Rust library in Godot (including tokio and async rust if you really want)
https://godot-rust.github.io/
Just don't forget the versioning script needed on at least Linux. It's either that or build with the same older distro Godot uses, so you have a matching libstdc++ version. You can link with a newer stdlibc++ but you will need a linker versioning script that hides your impl from the dynamic linker so you don't get random ghosts in your machine.
Hi! Yes, you are right, thanks for pointing this out. It's something to keep in mind when distributing an extension for Linux. I have just updated the post with a note about it.
A bit tedious but that's how it goes.
So, is a zero-copy impossible due to world (C++ vs Godot) boundaries?