How to redirect any url to index.html?

[Koki]

I build my website and deploy on GAE today.

I can access the homepage by:

https://koki-6hats.appspot.com/index.html

For other cases like:

https://koki-6hats.appspot.com/index

https://koki-6hats.appspot.com/

https://koki-6hats.appspot.com/shouldGoToIndex.html

is not worked. 

How do I config to make sure all links like above can redirect to index.html automatically?

[Yasser Karout (Cloud Platform Support)]

I noticed you have the same question posted on another thread. I will continue posting on the other one since it already has an active discussion on it.