For now, golang only.

But I am working on other supports.

Is there any common format for flamegraph (stacks), or should I do the work for all tools and languages?

https://www.brendangregg.com/flamegraphs.html

So if you can make your tool eat whatever https://github.com/brendangregg/FlameGraph is fed with you're going to support a lot of existing tooling across OSes and languages.