Where can find the golding Magikarp in Pokemon heart gold?

You can't find a Golding Magikarp in Pokémon HeartGold! There is no special "Golding" Magikarp variant in the game.

It's possible you're thinking of a different Pokémon or a different game. Maybe you're thinking of:

* Shiny Magikarp: These have a very rare chance of appearing in the wild, and they're a different color.

* A different game: Certain Pokémon games might have special variants or events that feature unique Magikarp.

Let me know if you can provide more details, and I'll do my best to help you find what you're looking for!