So, I recently installed Ubuntu 18.04 LTS on my 2014 Macbook Air 13inch (no dual boot). When I close the lid, the apple logo is still lit and the screen stays on. Because of this I usually press command L (super L) and then the computer will sleep. When I press a key to wake it afer, sometimes it wakes immediately but most of the times I have to wait around thirty seconds for the screen to turn on. Why?!?