2 things to note:
Firstly, this is the expected behaviour on iOS apps. Apps run in the background, until the user double presses the home key, and then kills the process from the bar at the bottom. Some apps will restart completely when you suspend and resume the app (such as clash of clans), but in my experience most of them don’t.
Do you just want to do this for testing purposes? If so that is fine, if not then make sure there is a good reason for it. It is not very convenient for the user if they are force to restart the app every time they leave and come back.
Secondly, how to make it restart each time:
Add this to your build.settings file:
settings = { iphone = { plist = { --this line kills the app whenever it is closed UIApplicationExitsOnSuspend = true, } } }