Solution Review: Longest Continuous Balanced Parenthesis

package main
import "fmt"
func longestContBalParen(str string, size int) int {
    stk := new(Stack)
    stk.Push(-1)
    length := 0
    for i := 0; i < size; i++ {
        if (str[i] == '(') {
            stk.Push(i)
        } else // string[i] == ')'
        {
            stk.Pop()
            if (stk.Length() != 0) {
                if length < i - stk.Top(){
                    length = i - stk.Top()
                }
            } else {
                stk.Push(i)
            }
        }
    }
    return length
}
// Testing code
func main() {
  expn := "())((()))(())()(()"
  size := len(expn)
  value :=longestContBalParen(expn, size)
  fmt.Println("longestContBalParen :: " , value)
}