module Main ( main ) where import Control.Concurrent (forkIO, threadDelay) import Control.Concurrent.STM (atomically, newTQueueIO, newTVarIO, readTQueue, readTVar, writeTVar) main :: IO () main = do continue <- newTVarIO True queue <- newTQueueIO forkIO $ do putStrLn "Start" atomically $ do continue' <- readTVar continue if continue' then readTQueue queue else pure () putStrLn "Finish" threadDelay 1000000 atomically $ writeTVar continue False pure ()