Use pooling and add a general Reader record to the stack by default

src/Main.hs

@@ -9,6 +9,7 @@ import Data.List
 import Effectful
 import Effectful.Error.Static   (Error, runError, runErrorNoCallStack, throwError)
 import Effectful.FileSystem
+import Effectful.Reader.Static
 import Network.Wai.Handler.Warp (run)
 import Servant hiding           ((:>), throwError)
 import qualified Servant        as S
@@ -17,22 +18,27 @@ import qualified Servant        as S
 -- Application
 --
 main :: IO ()
-main = run port $ serve proxy app
+main = do
+  pool <- createConnectionPool
+  let env = AppEnv { pool = pool }
+  run port $ serve proxy $ app env
 
-app :: Server AppAPI
-app = α $ rootHandler
+app :: AppEnv -> Server AppAPI
+app env = transformEff env 
+        $ rootHandler
      :<|> userListHandler
      :<|> userGetHandler
      :<|> userPostHandler
 
-α :: ServerT AppAPI AppEff -> ServerT AppAPI Handler
-α = hoistServer proxy 
+transformEff :: AppEnv -> ServerT AppAPI AppEff -> ServerT AppAPI Handler
+transformEff env = hoistServer proxy 
   $ Handler 
   . ExceptT 
   . runEff 
   . runErrorNoCallStack
   . runLoggerIO
   . runFileSystem
+  . runReader env
   . runDatabaseIO
 
 port :: Int