How can I use geometry instancing?

I write gemetry code head like this for output 120 polygon over.
I think it is possible to output maxvertexcount over number polygon with geometry instancing.

[maxvertexcount(120)]

[instance(32)]

void geom(triangle d2g vg[3], inout TriangleStream<g2f> outStream,uint gsid : SV_GSInstanceID)

But it not work, it output 120 only polygon.
What should I do for using geometry instancing?

If possible,please give me sample code.

 

It actually working.
geometory instancing increace to call geometry shader times,not maxvertexcount.