Improving Haskell code performance of this particular piece of code

I've used BangPatterns, Lazy ByteString. Don't know what else to do to improve performance of this code. Any ideas and suggestions?

-- Find the sum of all the multiples of 3 or 5 below N
-- Input Format 
-- First line contains T that denotes the number of test cases. This is followed by T lines, each containing an integer, N.

{-# LANGUAGE BangPatterns #-}
{-# OPTIONS_GHC -O2 -optc-O2 #-}
import qualified Data.ByteString.Lazy as L
import Control.Monad (mapM_)

readInt :: L.ByteString -> Int
readInt !s = L.foldl' (\x c -> 10 * x + fromIntegral c - 48) 0 s

main :: IO ()
main = do 
-- don't need the number of inputs, since it is read lazily.
-- split input by lines
  (_:ls) <- L.split 10 `fmap` L.getContents
-- length ls <= 10^5
  mapM_ (print . f . readInt) ls

-- n <= 10^9
f :: Int -> Int
f n = go 0 0
  where
    go !i !a | i == n            = a
    go !i !a | i `mod` 3 == 0
               || i `mod` 5 == 0 = go (i+1) (a+i)
    go !i !a                     = go (i+1) a