在Go中将变量括在方括号中

I am battling to understand what the (*s) does and I would appreciate an explanation.

// pop pops the stack. It will panic if s is empty.
func (s *nodeStack) pop() *Node {
    i := len(*s)
    n := (*s)[i-1]
    *s = (*s)[:i-1]
    return n
}

s is a pointer. *s is the thing it points to. The parentheses are to make clear -- both to the parser in the compiler, and to the human reader -- which one is being specified for array-style indexing. That is, it's to disambiguate between:

(*s)[i-1]

and

*(s[i-1])