Rounded Tooltip Border

I had used Table panel inside the tooltip. I need to change square border to Rounder border. How to achieve this?
I need border like below screen shot.

Borders are created by having a Shape surround an element, which in your case may be a “Table” Panel. That is accomplished with an “Auto” Panel:

  $(go.Adornment, "Auto",
    $(go.Shape, "RoundedRectangle", . . .),
    $(go.Panel, "Table",
      . . . various elements in rows and columns . . .

It’s working to me. Thanks…