Awesome but how to get the gold coins? – World War Z Review

The movie and the game really have things in common, but I heard someone said the ending was about you dying and becoming a Z "zombie" which is a part of sadness, but where do you get the gold coins? I mean they have a shotgun and melee weapons with the gold coin and they do look powerful, but they cost gold coins and you can't get them, I believe you got to buy the gold coins online, not cool about the gold coins but an awesome game.
Review by Covenant Hunter on World War Z.