A_array = append(A_array, B_array...)

A_array = append(A_array, B_array...)         ...  <-중요하다

package main
import "fmt"
func main() {
       //만약 cap을 생략하면  == len
       var A_array = make([]int, 10)
       var B_array = make([]int, 5)

       for i:=0; i<5; i++ {
              A_array[i] = i*2
       }
       fmt.Println("======== 1 STEP ========= ");
       for s:=0; s<5; s++ {
              fmt.Printf("A_array[%d] = %2d \n",s , A_array[s])
       }
       for k:=0; k<len(B_array); k++ {
              B_array[k] = k*4
       }

       A_array = append(A_array, B_array...)

       fmt.Println("======== 2 STEP ========== ");
       for j:=0; j<len(A_array); j++ {
              fmt.Printf("A_array[%d] = [%d] \n", j, A_array[j])
       }
}

맨마지막을 기준으로 채워진다.

======== 1 STEP =========
A_array[0] =  0
A_array[1] =  2
A_array[2] =  4
A_array[3] =  6
A_array[4] =  8
======== 2 STEP ==========
A_array[0] = [0]
A_array[1] = [2]
A_array[2] = [4]
A_array[3] = [6]
A_array[4] = [8]
A_array[5] = [0]
A_array[6] = [0]
A_array[7] = [0]
A_array[8] = [0]
A_array[9] = [0]
A_array[10] = [0]
A_array[11] = [4]
A_array[12] = [8]
A_array[13] = [12]
A_array[14] = [16]