Gtk Spinner Not Appearing

[yadmtr]

In this example Spinner Not Appearing: (Julia 1.5.3)

using Gtk
btn = GtkButton("Start")
sp = GtkSpinner()
ent = GtkEntry()

grid = GtkGrid()
grid[1,1] = btn
grid[2,1] = sp
grid[1:2,2] = ent
id = addprocs(1)[1]
signal_connect(btn, "clicked") do widget
 start(sp)
 @Gtk.sigatom begin
   @async begin
    s = @fetchfrom id begin
      sleep(4)
      return "I am back"
    end
    @Gtk.sigatom begin
      stop(sp)
      set_gtk_property!(ent,:text,s)
    end
  end
 end
end
win = GtkWindow(grid, "Progress Bar", 200, 200)
showall(win)