I wrote some machine learning tools in Go and the experience is quite bad. The lack of operator overloading and parametric polymorphism make most ML code ugly. It also does not help that Go's compiler backend does not optimize very strongly and calling out to C comes with a relatively large overhead.

Sure, I could use something like Haskell, but then I'd have to worry about whether I'm accumulating a giant stack of thunks that'll blow up.

There are many languages between Go and Haskell that are productive and provide a sufficiently strong type system.