addTrailingSlash :: W.Request -> Maybe ByteString
addTrailingSlash req
    | S8.null rp = Just "/"
    | S8.last rp == '/' = Nothing
    | otherwise = Just $ S8.snoc rp '/'
  where
    rp = W.rawPathInfo req
addTrailingSlash :: W.Request -> Maybe ByteString
addTrailingSlash req
    | S8.null rp = Just "/"
    | S8.last rp == '/' = Nothing
    | otherwise = Just $ S8.snoc rp '/'
  where
    rp = W.rawPathInfo req
addTrailingSlash req
    | S8.null rp = Just "/"
    | S8.last rp == '/' = Nothing
    | otherwise = Just $ S8.snoc rp '/'
  where
    rp = W.rawPathInfo req