the counter handled by stateT isn't changing with modify (+1)

gistfile1.txt

#!/usr/bin/env stack
-- stack --install-ghc runghc --package turtle
{-# LANGUAGE OverloadedStrings #-}

import Prelude hiding (FilePath)
import Turtle
import Control.Monad.State
import Data.Text
import Filesystem.Path.CurrentOS
import Data.Either
import Data.Either.Utils

main = view $ ((flip runStateT) 0) $ filePathProducer baseDirectory

baseDirectory = Filesystem.Path.CurrentOS.fromText "."

filePathProducer path = do
    child <- lift $ lstree path
    modify (+1)
    i <- get
    if (i `mod` 3 == 0)
                then (lift . echo) "**********************************"
                else (lift . echo . Data.Text.pack . show) i
    (lift . echo . fromRight . toText) child

sample output:

[1 of 1] Compiling Main ( ../ii.hs, interpreted )
Ok, modules loaded: Main.
*Main> main
1
./a1
((),1)
1
./a2
((),1)
1
./a3
((),1)
1
./a4
((),1)
1
./a5
((),1)
1
./a6
((),1)
1
./b/b1
((),1)
1
./b/b2
((),1)
1
./b/b3
((),1)
1
./b/b4
((),1)
1
./b/b5
((),1)
1
./b/b6
((),1)
1
./b/c/c1
((),1)
1
./b/c/c2
((),1)
1
./b/c/c3
((),1)