Simple gui app with threadpool

[elo]

Hi. I'm trying to make a simple gui app that performs functions at the press of 
a button. Of course, func is called in the main thread, so gui is freezing. I 
tried use the threadpool module, but I do something wrong. From what I 
understood, to read the result from thread, I have to use ^, but this causes 
freezing gui. When I calls without ^ works well, but how then read return? This 
is my simple code, I used nigui.
    
    
    import strutils
    import threadpool
    import nigui
    import os
    
    app.init()
    
    var window = newWindow("Win")
    window.width = 600.scaleToDpi
    window.height = 400.scaleToDpi
    
    var container = newLayoutContainer(Layout_Vertical)
    window.add(container)
    
    var button = newButton("Start")
    var textArea = newTextArea()
    container.add(button)
    container.add(textArea)
    
    proc doSomthing(time: int): string {.thread.} =
      sleep(time)
      return "end"
    
    button.onClick = proc(event: ClickEvent) =
      var t = spawn doSomthing(5000)
      textArea.addLine(^t)
    
    
    window.show()
    
    app.run()
    
    
    
    Run