Servant + postgresql-simple transactions (Handler vs. IO problem)

handler1.hs

handler1 :: String -> Handler c
handler1 emailToken = liftIO $ withTransaction conn $ do
  res1 <- findEmailTokenInDB emailToken  :: IO a
  if !foundToken(res1)
    then (throwError $ err401) -- not an IO operation
    else (do
      deleteToken emailToken :: IO b
      authenticateUser :: IO c
    )