If you're familiar with Node.js promises, you already know how it works. I just pass a hollow "DB" object to my controllers that can perform queries and commands, but instead of returning data imperatively, I use JS-like "promises" to chain the next steps. On the "success" callback you have the result of queries. At the end I will just return this "chain of statements" that wasn't executed yet. I only really run everything at the "imperative" layer, within a database transaction.

  return DB.Query(...).ThenCommand(res => ...).ThenHttpSuccess(res => ...);

That's also similar to how Haskell IO works. If you desugar the "do" syntax, you get something like this. Of course I said "monadic" between quotes above because it doesn't follow the functor/monad laws, it's just a Fluent interface promise-thing tailor-made for that very small app.

A big issue is that this was in very small project. Promises are not exactly pretty, and the code is not the easiest to maintain if you don't know how they work, which is why I "cheated" on the Golang app. I think someone else smarter might be able to figure this problem out too, though :)