[Dev]: Deadlocks

[TylerBloom]

I thought that I was careful and avoided opportunities for deadlocks. I was incorrect. Both DashMap::get() and DashMap::get_mut() can deadlock, which are used extensively. This should be rare but was the core issue behind #23. Either a more measured approach to acquisition needs to be implemented or those maps need to be swapped for an async type.

[TylerBloom]

A decent alternative to DashMap would be tokio::sync::RwLock<HashMap>. This would allow for all maps to be fully async.

[TylerBloom]

Because the throughput required of any given item in a DashMap is at most on the order of 100 requests per hour, a simple async spin lock should suffice. See b60bbe4 for the implementation of said spin lock.

[TylerBloom]

This was almost entirely addressed in dc426c9. There is still one outstanding issue that doesn't have an apparent solution. DashMap::insert can cause a deadlock; however, it doesn't have a 'try' counterpart like the get methods. So, a spin lock can't be used. The chances of this causing problems are very small.