You don't need a "readInt" - you just read a string, and then parse it into an int.
import std/strutils stdout.write "Enter a number: " try: let num = parseInt(stdin.readLine()) except ValueError: echo "That's not a number!" Run
import std/strutils stdout.write "Enter a number: " try: let num = parseInt(stdin.readLine()) except ValueError: echo "That's not a number!"