long running task in shiny with task in global future

shinyglobalpromise.R

library(shiny)
library(DT)
library(dplyr)
library(future)
library(promises)
plan(multiprocess)

ui <- fluidPage(
    verbatimTextOutput("timer"),
    DTOutput("myTable")
)

#time stamp
observe({
  invalidateLater(1000, NULL)
  print(Sys.time())
})

#initial value
rlist <- reactiveValues()
rlist$tbl_vals <- tibble(Value = rnorm(5))

#set up global observer
observe({
  print("observer running")
  future ({get_data()}) %>%
    then(function(got_data){
      isolate({rlist$tbl_vals <<- got_data})
      invalidateLater(3000, NULL)
      print("now returning data from future")
    })
})


server <- function(input, output, session){


#second timer
    output$timer <- renderText({
      invalidateLater(1000, session)
      as.character(Sys.time())
    })


    output$myTable <- renderDT({
      rlist$tbl_vals
    })

}

get_data <- function(){
    expensive_operation()
    tibble(Value = rnorm(20))
}

expensive_operation <- function(){
    invisible(rnorm(100000000))
}

shinyApp(ui, server)