为什么有时在paren中有返回值，而有时在Go函数签名中却没有？

Question

I noticed that Go function signatures sometimes have a return value in parentheses, and sometimes do not. Is this just a matter of taste, or is there a deeper implication to choosing one over the other.

I've looked through the go documentation, and in go specs in blog articles etc, and not found anything conclusive to answer this question. Most function signature definitions I've come across gloss over this point, and that is why I believe the answer is nuanced.

  func Example(num int) (error){
    ..
  }

  func Example(num int) error {
    ..  
  }

Answer 1

If the function has one return value, it means the same thing with or without parentheses. Without parentheses is typically preferred.

If the function has more than one return value then parentheses are required.

func Example() (string, error) {
    return "", nil
}

If there are named return values, parentheses are also required.

func Example() (s string) {
    s = ""
    return
}