un9nplayer/SubTracker ? reverse-engineered prompt

Build me a cross platform command line tool in Go for discovering subdomains for a domain I give it.

I want it to start with a setup step where I can save my AgniOps API key securely, then run scans against a target domain and show the results in a clean terminal table with the subdomain, IP address, and whether it looks like it is behind Cloudflare. It should also let me export the same results as JSON, CSV, or plain text, and optionally save the output to a file.

Please include a simple update command that checks for new releases, a version flag, and a nice loading spinner while scans are running. It should show how many daily scans are left after each request, and it needs to work on Linux, macOS, and Windows. If you need to look up current docs online, go ahead.