Textile and construction in one gst

SAC codes will be different. You may want to update accordingly at GST portal.

As per Section 22 the person required take registration only at place from where he made supply. So there is no any such restriction of obtaining registration for every different line businesses.
Thus you can carry both textile & building contractor business under the same GSTN . But it is advisable to keep accounting easier & accurate you must obtain separate registration for both the business.