Google has now added a new API which will allow users to use the app even while updating it. Earlier one was not able to use the app while updating as it uses to force close the app but with this new API, one can use the app even while updating.
Google is calling the new API as In-app updates which are currently tested with few partner apps and soon after Beta phase, it will be made available to large Developers. Google in-app update comes in two forms one which uses the full-screen mode to update the app without using it whereas the other one can use the app while updating it.
As per the source, the in-display app update will provide full control to developers to implement it. We are still not sure about the release of new API but it might arrive with the next iteration of Android Q.