import System.IO (IOMode(..), hGetContents, openFile, openBinaryFile, utf8)

main =
  do h <- openBinaryFile "test-file.md" ReadMode
     hGetContentContents h
     -- Binary read works fine out-of-box.

     h' <- openFile "test-file.md" ReadMode
     hSetEncoding h' utf8
     hGetContentContents h'
     -- This works only if encoding is explicitly set, otherwise
     -- it gives "invalid byte sequence" error at run-time

export LANG=en_US.UTF8 cabal build