This question already has an answer here:
- Keep wi-fi connection while asleep? 2 answers
I have tested this with 2 iPhones, and one Samsung phone. Whenever I put close my Macbook (put it on sleep), and I open it again, I have to reconnect to my wi-fi. Initially the hotspot will not be discoverable. I have to go to my iPhone, turn off the Personal Hotspot slider, and turn it on again (effectively resetting it). Then it will be discoverable and I can connect to it. This happens with both iPhones. Both are iPhone 6. My Mac is running 10.11.
This does not happen with my Samsung phone at all.