If the internet goes down in the entire world, you will have much bigger problems than trying to use your bitcoins. Your gold will not be worth anything either. Food/medicine/essential goods will be what drives the demand by then. Some call it the apocalypse - other the end of the world.
But intill that day, bitcoin will thrive.
why you think gold not worth anything when disaster came? example in conflict zone atm precious metals(not only gold) still used as medium of exchange. When internet goes down in the entire world (gold already pass through that era) yes it will be bigger problem, but who will stand as medium of exchange when that moment come? is it paper money, gold or bitcoin?