You can write python, typescript, or many other languages. I prefer TS because it has curly braces and object deconstruction. I do a lot of devops things in python though, so there is appeal for adopting the python SDK in certain contexts. I agree that Go is not a great choice for builds or scripting more generally, but it does mean you can build Dagger into any Go CLIs you might have, which is intriguing for me in one project I have.

The experimental Dagger Modules allows interlanguage invocation. I'm not a huge fan of the current DX, a bit heavy for my monorepo setups, but once I can cleanly call them from the main entry based workflow, I can see consuming them.