There are so many proper ways I could respond here, but I’ll save them for a more deserving moment.

Your comment is even worse.

this only works cause uses a named return type. If his variable would be called sum1 it would return nothing.

Maybe its valuable to note that

out := ""

is the same as

var out string

which doesn't need to be initialized as the Zero Value of a String is by default ""

For example?

Depends on the situation and constraints

is fmt.Sprintf a good way to save a value?

Yeah, you're right

"You can assume, for the purpose of this kata, that the supplied array will not be empty"
we have this sentence in description.

what if numbers is empty?

This solution doesn't working with Unicode

Really interesting) I've never seen that we can just return w/out specifying the variable to return

Yes, here are some links with reasoning:

• PMD linting rule (Java)
• ESLint Linting rule no-param-reassign (JavaScript/TypesScript)
• ESLint Linting rule no-ex-assign (JavaScript/TypesScript)
• Software Engineering Stack Exchange about it
• GitBook about Java
• medium article "Why it’s bad practice to reassign function params"
• Answer on StackOverflow

If you need a variable later in the code, it's very easy to just make a copy. The problem is with arrays / pointers, with which there are side effects. But there are no inconvenients with integers AFAIK. Do you have any authorities to back up this?