Reload Unity view inside native iOS application.

I have integrate unity application inside my native application using the link below https://medium.com/@IronEqual/how-to-embed-a-unity-game-into-an-ios-native-swift-app-772a0b65c82

I am able to load unity view when I come to the view controller inside viewDidLoad method. Unity view is loaded first time correctly, but when I press back button from native iOS application and come back to the Unity view, Unity view is not loaded.

How do I load unity view again without kill the whole application.

Thanks in advance.