improve slightly

This probably avoids the situation that caused the exception to be
thrown. It also makes sure that both threads end up canceled in the end,
while before the exception from wait outt could have caused errt to
never be waited on.

Utility/Metered.hs

@@ -319,6 +319,7 @@ outputFilter cmd params environ outfilter errfilter =
 		outt <- async $ tryIO (outfilter outh) >> hClose outh
 		errt <- async $ tryIO (errfilter errh) >> hClose errh
 		ret <- waitForProcess pid
+
 		-- Normally, now that the process has exited, the threads
 		-- will finish processing its output and terminate.
 		-- But, just in case the process did something evil like
@@ -330,7 +331,10 @@ outputFilter cmd params environ outfilter errfilter =
 		-- openssh.)
 		void $ tryNonAsync $ race_
 			(wait outt >> wait errt)
-			(threadDelaySeconds (Seconds 2) >> cancel outt >> cancel errt)
+			(threadDelaySeconds (Seconds 2))
+		cancel outt
+		cancel errt
+
 		return ret
 	go _ _ _ _ = error "internal"