Use patterns for POSIX signals.

server/homepage.cabal

@@ -220,6 +220,7 @@ library
   other-modules:
     , Control.Monad.IO.Unlift.OrphanInstances
     , Control.Monad.Logger.OrphanInstances
+    , System.Posix.Signals.Patterns
     , Text.Blaze.Html5.Extra
   hs-source-dirs: source/library
 

server/source/library/Homepage/Server.hs

@@ -27,6 +27,7 @@ import Servant.API.Generic
 import Servant.Server
 import Servant.Server.Generic
 import System.Posix.Signals
+import System.Posix.Signals.Patterns
 
 type API :: Type
 type API = ToServantApi Routes
@@ -48,9 +49,9 @@ server = do
               logWarn "Shutdown."
             closeSocket
       let installShutdownHandler sig = void $ installHandler sig (catchOnceShutdown sig) Nothing
-      installShutdownHandler sigHUP
-      installShutdownHandler sigINT
-      installShutdownHandler sigTERM
+      installShutdownHandler SIGHUP
+      installShutdownHandler SIGINT
+      installShutdownHandler SIGTERM
   let settings = withShutdownHandler $ withPort defaultSettings
 
   logInfo "Configure middleware."

server/source/library/System/Posix/Signals/Patterns.hs

@@ -0,0 +1,26 @@
+{-# LANGUAGE PatternSynonyms #-}
+
+module System.Posix.Signals.Patterns where
+
+import System.Posix.Signals
+
+-- Source: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/kill.html
+-- Other signals are not defined by POSIX.
+
+pattern SIGHUP :: Signal
+pattern SIGHUP = 1
+
+pattern SIGINT :: Signal
+pattern SIGINT = 2
+
+pattern SIGQUIT :: Signal
+pattern SIGQUIT = 3
+
+pattern SIGABRT :: Signal
+pattern SIGABRT = 6
+
+pattern SIGALRM :: Signal
+pattern SIGALRM = 14
+
+pattern SIGTERM :: Signal
+pattern SIGTERM = 15