So you need to share an object between threads, what do you do?
Wrap it in an ArcMutex pointer and call it a day right?
Let's take it to the next level.
A very common pattern in rust is to hide the arc mutex pointer in an inner property and to implement the clone trait, that way you can just pass the object around by cloning it.
Just be careful, because every time you call a method in your SharedCache object you will be locking internally, which might lead to some race conditions.
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https://www.youtube.com/watch?v=Db2RzBV3IWQ