SlackBuildsOrg/haskell/haskell-async

This Haskell package provides a higher-level interface over threads,
in which an Async a is a concurrent thread that will eventually
deliver a value of type a. The package provides ways to create Async
computations, wait for their results, and cancel them.

After uninstalling, run this command to unregister the package from
the ghc package database:   ghc-pkg recache