func append(slice, element_1, element_2…, element_N) []T

package main
import "fmt"
func main() {

   // Initialize the multi-dimensional array
   arr := [][]int{
      {1, 2, 3, 4},
      {5, 6, 7, 8}, 
      {9, 10, 11, 12},
   }
   fmt.Println("The 2-D array is:", arr)

   // Flatten the array using the append function
   flatArr := flattenArray(arr)

   // Print the flattened array
   fmt.Println("The flattened array obtained from above multidimensional array is:", flatArr)
}
func flattenArray(arr [][]int) []int {

   // Initialize the flattened array
   flatArr := []int{}

   // Iterate through the rows of the array
   for _, row := range arr {

      // Append the current row to the flattened array
      flatArr = append(flatArr, row...)
   }
   return flatArr
}

The 2-D array is: [[1 2 3 4] [5 6 7 8] [9 10 11 12]]
The flattened array obtained from above multidimensional array is: [1 2 3 4 5 6 7 8 9 10 11 12]