retry
    :: forall m a. (MonadBaseControl IO m, MonadResource m)
    => Int -- ^ sleep count
    -> Int -- ^ number of retry
    -> EC2 m a
    -> EC2 m a
retry _   0   f = f
retry
    :: forall m a. (MonadBaseControl IO m, MonadResource m)
    => Int -- ^ sleep count
    -> Int -- ^ number of retry
    -> EC2 m a
    -> EC2 m a
retry _   0   f = f
retry _   0   f = f