Dumb formula question...

Hayley • ~IT'S A GIRL!! 💕baby # 2 due May/June 2019~ 💙William Jack 17-08-17 💙
So I'm due in August and was just wondering if I should buy formula just in case I can't breastfeed? I'm hoping to b/f exclusively but should you just keep some formula on hand on the chance that I can't? Thanks