On line 7, it is concluded that the internal array will be overflowed and a new one will be created. Why did you decide that?

In Go, slices have an underlying array that stores the data. When you append an element and the current underlying array is full, a new array with increased capacity is created, and the data is copied there.

On line 7, it is likely that an append is happening to a slice that has already reached its capacity. Therefore, a new array is created to accommodate additional elements.

This behavior can be verified as follows:

s := make([]int, 0, 2) // length 0, capacity 2
s = append(s, 1, 2)     // now length 2, capacity 2
s = append(s, 3)        // capacity is insufficient, a new array is created

Thus, the conclusion about creating a new array is based on understanding the internal implementation of slices in Go and observing that the length has reached the capacity.