Code snippet works in an online IDE but not on my local ghc

Question

As a beginner, i wrote a snippet to flip a string's case.

module Main
 where

import Data.Char

main=do
  str<-getLine
  putStrLn ( reverser(str) )

reverser:: String -> String 
reverser [] = []
reverser (x:xs) | isUpper x = toLower x : reverser xs
                | otherwise = toUpper x : reverser xs

And it worked perfectly on the hackerearth.com's IDE

IDE screenshot

However,when I tried running the same on my machine, the code is executing endlessly and not coming up with any output nor error.

Terminal

What am I doing wrong?