Gst for freelancer having other income

Hi

I am an freelancer software developer with annual turnover less than 20 Lacs per annum. 

For previous assessment year, my income from business was 17 lacs and income from commercial property rent was 4 lacs. 

My query is that am I required to get a GST number because total income was more than 20 lacs? Since commercial property rent is not the nature of my business and just an income earned from my asset, I feel it should not count as turnover towards GST limit for individual. 

Please let me know if I can avoid GST registration or not?