GHC supports Concurrent Haskell by default, without requiring a
special option or libraries compiled in a certain way. To get access
to the support libraries for Concurrent Haskell, just import
Control.Concurrent (details are in the accompanying
RTS options are provided for modifying the behaviour of the threaded runtime system. See Section 4.12.4, “RTS options for Concurrent/parallel Haskell ”.
Concurrent Haskell is described in more detail in the documentation