Might be a stupid question... milk

Hi ladies. Im just trying to organise my hospital bag and on all my helpful notes about what to bring doesnt say formula. I am planning on breastfeeding but as a 1st timer im worried for some reason my boobs just wont work. Do people tend to take formula just on the safe side? My other worry is say i cant breastfeed straight away and baby does need formula will they want to go back to boob. All very new to us so any advice is welcome x