Gst on work contract

What is the Gst rate for Government contractor ? 

6 % or 12 %,

My tender passed before Gst, but the work done and payment received in Gst tenor ,

My work schedule is of Vat, old Schedule,

What is the Gst Rate for Government contractor ?

My turnover is below 20 lakhs and I am registered with Gst ,

I think no Gst below 20 lakhs,

Please Clarify