With regards to the leaking issue - that's not actually correct. `Box::leak` does not give you access to the context with the `'static` lifetime, assuming the lifetime of the context is not 'static (that would fundamentally break rust's safety guarantees).
The only potential problem is that the destructor for the context may not run (cf. leakpocalypse). If the implementation requires the destructor to run, then you are right, you should never give ownership of the context object, it should be passed into the callback by reference. If you need access to a context outside of a callback, then you should use the callback-style:
with_context(|ctx| {
... do stuff ...
}
The nice thing is that `with_context` can enforce any threading constraints you might have (like contexts being accessed from a single thread), can ensure that the context is safely dropped at the end, and it's only required once - once you have a context you can use it as many times as you need.