I really like Go for its simplicity, ecosystem, and ability to develop applications and libraries in rapid, understandable ways. In particular it is easy to integrate Go applications and libraries with anonymous networks thanks to libraries like goSam, sam3, and bine. Obviously in the browser JavaScript is the only way to fly. Brief love affairs with various JS transpires taught me I should just get better at JavaScript.

depends are you designing are a tor based website or clearnet?

There's a lot of ways to start doing this. I started out with Python, and I was able to pick up on Flask and Django pretty quickly. Both are fantastic libraries to create websites with, but I think learning Node.js and express is also another great combo for making websites. (This applies to Clearnet sites, not 100% sure about Tor based websites)