Append Result Not Assigned Back to Slice

Why This Happens

Go's append function may need to allocate a new underlying array if the slice's capacity is exceeded. It returns the updated slice header, which may point to a new array. If you do not assign the result, the appended element is lost.

The Problem

func main() {
    s := []int{1, 2, 3}
    append(s, 4) // result not assigned
    fmt.Println(s) // still [1 2 3]
}

The Fix

func main() {
    s := []int{1, 2, 3}
    s = append(s, 4)
    fmt.Println(s) // [1 2 3 4]
}

Step-by-Step Fix

1. 1

   Identify the unassigned append

   Find the append call whose result is not being assigned to any variable.

2. 2

   Assign the result

   Write s = append(s, items...) to capture the potentially new slice.

3. 3

   Verify the behavior

   Check that the slice reflects the new elements after the append.