Launch service thread with a function that re-throws if they fail

In Haskell by default if a thread has an exception, the main thread isn't
notified at all. This patch changes service thread launching to re-throw their
exceptions in the main thread, so that their failure is noticed.

src/Vervis/Application.hs

@@ -1,6 +1,6 @@
 {- This file is part of Vervis.
  -
- - Written in 2016, 2018 by fr33domlover <fr33domlover@riseup.net>.
+ - Written in 2016, 2018, 2019 by fr33domlover <fr33domlover@riseup.net>.
  -
  - ♡ Copying is an act of love. Please copy, reuse and share.
  -
@@ -30,7 +30,6 @@ module Vervis.Application
     )
 where
 
-import Control.Concurrent (forkIO)
 import Control.Monad.Logger                 (liftLoc, runLoggingT, logInfo, logError)
 import Database.Persist.Postgresql          (createPostgresqlPool, pgConnStr,
                                              pgPoolSize, runSqlPool)
@@ -54,6 +53,10 @@ import Yesod.Mail.Send (runMailer)
 
 import qualified Data.Text as T (unpack)
 
+import Control.Concurrent.Local (forkCheck)
+
+import Vervis.ActorKey (generateActorKey, actorKeyRotator)
+
 -- Import all relevant handler modules here.
 -- Don't forget to add new modules to your cabal file!
 import Vervis.Handler.Common
@@ -229,10 +232,10 @@ appMain = do
     app <- makeApplication foundation
 
     -- Run SSH server
-    forkIO $ sshServer foundation
+    forkCheck $ sshServer foundation
 
     -- Run mailer if SMTP is enabled
-    forkIO $ mailer foundation
+    forkCheck $ mailer foundation
 
     -- Run the application with Warp
     runSettings (warpSettings foundation) app