Make gFromEnv return Either String (...)

app/Main.hs

@@ -37,6 +37,7 @@ import Servant
   , (:>)
   , pattern MkHandler
   )
+import System.Exit (exitFailure)
 import System.FilePath ((</>))
 import Text.Blaze.Html.Renderer.Utf8 (renderHtml)
 import Text.Blaze.Html5 ((!))
@@ -80,8 +81,13 @@ deriving instance Show Config
 
 main :: IO ()
 main = do
-  cfg <- Envy.load @ConfigT
-  -- _ <- exitSuccess
+  cfg <-
+    Envy.load @ConfigT >>= \case
+      Left err -> do
+        Log.error $ printf "failed to read config: %s" err
+        exitFailure
+      Right c ->
+        pure c
 
   let
     settings =
@@ -95,7 +101,7 @@ main = do
         ]
 
   db <- DB.initDB cfg.yoreDb
-  Warp.runSettings settings $ serve (Proxy :: Proxy API) $ hoistServer (Proxy :: Proxy API) nt $ server cfg db
+  Warp.runSettings settings $ serve (Proxy @API) $ hoistServer (Proxy @API) nt $ server cfg db
   where
     logger req status _ = do
       Log.info $