Xcode playground gets stuck on 'Running playground' or 'Launching simulator' and won't run the code, what to do?

Question

Every time I create a new playground in order to test some code, Xcode gets stuck and won\'t run the code. It simply presents \'Running playground\' or \'Launching simulator

Answer 1

Also happens, like in my case, when you've defined a function, but have forgotten to call it?