Because people hear that Go supports value types and so is more efficient than Java because it can allocate on the stack*, and so they start thinking that they need to manage the stack.

* Of course, in reality, Java also does escape analysis to allocate on the stack, though it's less likely to happen because of the lack of value types.

I don't see the difficulty here. The slice is to be thought of as value type, as demonstrated in the C version. Just like in C, you can return it from a function without the heap because it is copied.