func TestSlice(t *testing.T) { s := make([]any, 0, 2) s = append(s, 1, 2) // 1 2 len(2) cap(2) modifySlice(s, 3) log.Printf("1: %+v", s) sPtr := unsafe.Pointer(unsafe.SliceData(s)) a := (*[10]any)(sPtr) log.Printf("2: %+v", *a) // 0 0 3 <nil>.... s = append(s, 4) log.Printf("3: %+v", s) // 0 0 4 } func modifySlice(s []any, v any) { s = append(s, v) s[0] = 0 s[1] = 0 }