fix: shutdown should wait for in flight requests

Upgraded warp to 3.4.13 which fixed https://github.com/yesodweb/wai/issues/853
Changed interrupt handling so that instead of killing the main thread, listening sockets are closed which triggers warp graceful shutdown.

src/PostgREST/App.hs

@@ -22,6 +22,7 @@ import GHC.IO.Exception (IOErrorType (..))
 import System.IO.Error  (ioeGetErrorType)
 
 import Control.Monad.Except     (liftEither)
+import Control.Monad.Extra      (whenJust)
 import Data.Either.Combinators  (mapLeft, whenLeft)
 import Data.Maybe               (fromJust)
 import Data.String              (IsString (..))
@@ -79,8 +80,10 @@ run appState = do
 
   AppState.schemaCacheLoader appState -- Loads the initial SchemaCache
   (mainSocket, adminSocket) <- initSockets conf
-
-  Unix.installSignalHandlers observer (AppState.getMainThreadId appState) (AppState.schemaCacheLoader appState) (AppState.readInDbConfig False appState)
+  let closeSockets = do
+        whenJust adminSocket NS.close
+        NS.close mainSocket
+  Unix.installSignalHandlers observer closeSockets (AppState.schemaCacheLoader appState) (AppState.readInDbConfig False appState)
 
   Listener.runListener appState