That's basically how the Go WASM runtime works[1], except when calling outside the WASM virtual machine (e.g. invoking a JavaScript function) the entire Go runt

That's basically how the Go WASM runtime works[1], except when calling outside the WASM virtual machine (e.g. invoking a JavaScript function) the entire Go runtime must block. [1] The Go compiler inserts yield calls (preemption opportunities) at various points in the emitted code, such as at function invocations and within loops.