title: Why a component from andlabs/ui package is not found
body: <p>I am trying following simple code (modified from <a href="https://github.com/andlabs/ui/wiki/Getting-Started" rel="nofollow noreferrer">here</a>) to create a window: </p>
  
  <pre><code>package main
  import ("github.com/andlabs/ui")
  func main() {
      ui.Main(makeMainWin)
  }
  func makeMainWin(){
      var bmiButton = ui.NewButton("First")
      var otherButton = ui.NewButton("Second")
      //ui.NewVerticalStack does not work; 
      stack := ui.NewVerticalStack(
                  ui.NewLabel("Select module"),
                  bmiButton,
                  otherButton,
                  )
      var mainWindow = ui.NewWindow("Hello", 200, 100, stack)
      mainWindow.OnClosing( func (*ui.Window) bool { ui.Quit(); return true   } )
  }
  </code></pre>
  
  <p>However the code is not compiling and I am getting following error: </p>
  
  <pre><code># command-line-arguments
  ./guiStack.go:14:11: undefined: ui.NewVerticalStack
  </code></pre>
  
  <p>Why it is not able to find NewVerticalStack?
  Where is the problem and how can it be solved? Thanks for your help.</p>