Note: As of Shiny 1.5.0, we recommend using moduleServer() instead of
callModule(), because the syntax is a little easier
to understand, and modules created with moduleServer can be tested with
testServer().
callModule(module, id, ..., session = getDefaultReactiveDomain())A Shiny module server function
An ID string that corresponds with the ID used to call the module's UI function
Additional parameters to pass to module server function
Session from which to make a child scope (the default should almost always be used)
The return value, if any, from executing the module server function