golang append() evaluated but not used

Question

func main(){
     var array [10]int
     sliceA := array[0:5]
     append(sliceA, 4)
     fmt.Println(sliceA)
}

Error : append(sliceA, 4

Answer 1

The key to understand is that slice is just a "view" of the underling array. You pass that view to the append function by value, the underling array gets modified, at the end the return value of append function gives you the different view of the underling array. i.e. the slice has more items in it

your code
sliceA := array[0:5]  // sliceA is pointing to [0,5)
append(sliceA, 4) // sliceA is still the original view [0,5) until you do the following

sliceA = append(sliceA, 4)

reference: https://blog.golang.org/slices