Getting the waiter function to run before a R Shiny apps UI comes up

I am working on a R Shiny app and we are using the Waiter package to display a loading screen while data is read in that is used in tables/graphs. The problem is that the UI pops up for an instant before the waiter function begins working. Is there any way to have the waiter loading screen be the first thing that appears? (i.e. how do I avoid having the UI pop up for a second before the loading screen starts?)