IsGST return mandatory for independent contractor (software engr working for a startup based in USA

Namaste friends, I am a software engineer working as a independent contractor for a startup based in USA. This company has no India presence. They are paying me more than 20Lakhs/year. I am filing my income tax return. Should I file GST return too? My IT bracket is 30% + GT 18%. Am I supposed to 50% tax to GOI? Thank you.