Add lock to protect concurrency

[Taction]

When I test wasi-http in dapr, I found there was still concurrent map writes errors: https://github.com/dapr/components-contrib/actions/runs/5851405294/job/15862279360?pr=3077. I have tried using the latest sdk version in my local enviroment, but this issue still appears.

So I added lock to protect the map since there could be multi wasm instances, this works fine in my local environment.

also related to #87

[brendandburns]

This code looks good to me, but I actually think I may have written the test wrong...

I will look at the dapr test and see if there's a way to fix it there also.

[brendandburns]

I looked into this somewhat, and here are the details.

In the Dapr codebase, NewRuntimeWithConfig is called in the Init function: https://github.com/dapr/components-contrib/blob/master/bindings/wasm/output.go#L73 The module is also compiled in Init

And then the module is instantiated in Invoke which I believe can run in parallel: https://github.com/dapr/components-contrib/blob/master/bindings/wasm/output.go#L136

I realized that I'm not perfectly clear about this comment: https://github.com/stealthrocket/wasi-go/issues/87#issuecomment-1644768227

Does it imply that a Runtime can be used concurrently for multiple InstantiateModule calls? If so, this PR is the right fix.

If not, the right fix is in the Dapr codebase.

[brendandburns]

~Given that a Runtime has an associated Store (https://github.com/tetratelabs/wazero/blob/main/RATIONALE.md#runtime--enginestore) I think that implies that a Runtime should not be multi-threaded, but I'm still not positive.~

I take it back this is documented in wazero here: https://github.com/tetratelabs/wazero/blob/main/examples/concurrent-instantiation/main.go

[brendandburns]

Ok, after a little more research, I believe that this fix is correct for concurrent execution of multiple instantiated modules in the same Runtime

Thanks!

[Taction]

Thanks for your patience and the research. In my humble opinion, using multi runtime instances would consume more (memory mainly) resources than instantiated multi wasm instances. And using one wasm instance which means handling requests one by one is not acceptable in the production environment.

[brendandburns]

@achille-roussel I think this is fine to merge whenever you get a chance.

Thanks!