Consider `im` in conjunction with `AtomicPtr` instead of `concread`

[GregoryConrad]

Not sure if this would actually bring any performance improvements, but it is possible it could since the implementation would be entirely lock-free and im has some interesting optimizations. A benchmark would be required.

I doubt I'm going to work on this much, but would be open to PRs.

[GregoryConrad]

Just realized this actually won't make much sense since writes would still need to be guarded by a lock to prevent overwrites