unexpected slice append behaviour

Question

I encountered weird behaviour in go code today: when I append elements to slice in loop and then try to create new slices based on the res

Answer 1

There is also a little bit simpler way to implement copyAndAppend function:

func copyAndAppend(source []string, items ...string) []string {
    l := len(source)
    return append(source[:l:l], items...)
}

Here we just make sure that source has no available capacity and so copying is forced.