What will happen if we add too many elements to a slice inside a function?

In Go, a slice is a structure that contains a pointer to an array, a length, and a capacity. If you add too many elements to a slice, exceeding its current capacity, Go will automatically allocate a new larger array and copy the data.

This means that when adding elements, the slice may be reallocated, which leads to additional time and memory costs. If you add elements to a slice inside a function without returning the new slice, the changes may not be saved because slices are passed by value (the structure is copied, but not the data).

Example:

func appendElements(s []int) {
    for i := 0; i < 1000; i++ {
        s = append(s, i) // a new slice is created when capacity is exceeded
    }
}

// To save changes, you need to return the slice:
func appendElementsCorrect(s []int) []int {
    for i := 0; i < 1000; i++ {
        s = append(s, i)
    }
    return s
}

Thus, when adding a large number of elements, it is important to consider memory reallocation and work correctly with the returned slice value.