Core Flatmap

Manipulates a slice and transforms and flattens it to a slice of another type. The transform function can either return a slice or a nil, and in the nil case no value is added to the final slice.

out := lo.FlatMap([]int64{0, 1, 2}, func(x int64, _ int) []string {
    return []string{strconv.FormatInt(x, 10), strconv.FormatInt(x, 10)}
})
// []string{"0", "0", "1", "1", "2", "2"}