Zooming with mouse wheel

How i can do Zoom in/out with mouse wheel in GOJS graph ?
Can you guide me here

This behavior is enabled by default if the user also holds down the control key.

If you want to have that behavior without the control key modifier, set ToolManager | GoJS API

$(go.Diagram, ...,
    "toolManager.mouseWheelBehavior": go.ToolManager.WheelZoom,
    . . .

I have added this line into my code
"toolManager.mouseWheelBehavior": go.ToolManager.WheelZoom,
go.ToolManager.WheelZoom, is not working on graph .
But this is not working in my div container in which i have render graph.

Can you suggest me why its not working?

Maybe we are talking about different things? There are a bunch of samples that set that property to WheelZoom. (Search for that string.) Do you have the expected behavior in those samples?

I just want to add Zoom in/out functionality on Graph using mouse wheel ,
can you guide me here

I have already given you the code. I referred you to many existing samples that do what I suspect you want, to confirm that that is indeed what you wanted.