Go语言中的[:]是什么意思呢？

package main

import "fmt"

func twoSum(nums []int, target int) []int { var result = [2]int {0,0} if len(nums) < 2 { return nil }

for i := 0 ; i < len(nums) - 1; i++ {
    for j := i + 1; j < len(nums); j++ {
        if(nums[i] + nums[j] == target){
            result[0] = i
            result[1] = j
            return result[:]  //我理解的是返回之前初始化的result数组，无论数组元素多少，都可以以[:]代替
        }
    }
}
return nil

}

func main() {

var num = [4]int{2, 7 ,11, 15}

fmt.Println(twoSum(num[:] ,9))

}