How do you get Hitmonchan in Pokemon Gold?

Find the Karate King inside Mt Mortar, he will give you a Tyrogue after you beat him (make sure you only have 5 Pokemon in your party). Raise the Tyrogue to level 20, if it has more attack than defence it evolves into Hitmonlee, if it has more defence than attack, hitmonchan, if they're even, hitmontop.