Attempt to use ExtendedTask + mirai with cancellation

app.R

library(shiny)
library(mirai)
library(promises)
library(bslib)

ui <- page_fluid(
  input_task_button("go", "Go"),
  actionButton("stop", "Stop"),
  textOutput("out")
)

server <- function(input, output, session) {
  mirai_obj <- NULL
  
  task <- ExtendedTask$new(function() {
    m <- mirai({
      Sys.sleep(5);
      "hello, world"
    })
    mirai_obj <<- m
    m
  }) |> bind_task_button("go")
  
  observeEvent(input$go, {
    task$invoke()
  })
  
  observeEvent(input$stop, {
    stop_mirai(mirai_obj)
  })
  
  output$out <- renderText({
    task$result()
  })
  
  observe({
    updateActionButton(session, "stop", disabled = !identical(task$status(), "running"))
  })
}

shinyApp(ui, server)