Cancel TQueue read

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 ()