You can build in wall brackets and cut custom shelves to fit the corner. We did this, but we did all straight cuts, but you could easily cut the boards at an angle! https://www.charlestoncrafted.com/complete-pantry-remodel/
Here is a video showing the basics plus a few tips when making shelving for walls. I hope this will help you as you start your research. Wishing you the best.
Here is a diy. https://www.hometalk.com/27941618/diy-corner-pantry