Any breast feeding experts?

I want to breastfeed and I’ve done a lot of research I’m just most worried about the 1st week of birth since some supplies take a bit to come in. Does the baby just not eat for those days? Do you give formula until supply comes in? Like it’s just scary to me i don’t want my child to wait 2 or 3 days to eat. Also I know they say colostrum will supplement the baby until supply comes in but how do you actually know the baby is even receiving that?