Hi Wasim, https://gophercises.com/ is a great resource to learn Go. Once you go through the basics of the language, the best way to master it would be building some applications. Start building things that matter to you. Maybe, something that solves a problem that you're having.
When it comes to choosing another tech stack, I would highly recommend learning JavaScript and TypeScript. There are many JS/TS based frontend and backend libraries out there. Some of them have a very high demand (React, Angular, Node.js, Express etc.). This will prepare you for a wider range of job opportunities.
Also, don't forget to master data structures, algorithms and design patterns. This will add more value to you as a developer.