go语言学习---二分查找

package main
import "fmt"

func upper_bound_ (v int, a[] int) int{
    len_a := len(a)
    left := 0
    right := len_a - 1
    for {
        mid := left + (right - left) / 2
        if a[mid] == v {
            return mid
        }else if a[mid] > v{
            right = mid - 1
        }else if a[mid] < v{
            left = mid + 1
        }

        if left > right {
            break
        }
    }
    return -1
}

func main() {
    a := [] int {1, 2, 3, 4, 5}
    fmt.Println(upper_bound_(6, a))
}