func Subtract(listA, listB []string) []string {
	list := make([]string, 0, len(listA))
	for _, item := range listA {
		if !Contains(listB, item) {
			list = append(list, item)
		}
	}
	return list
}
Subtract will return a list with items that are only part of the first list.
package stick
func Unique(list []string) []string {
	table := make(map[string]bool)
	res := make([]string, 0, len(list))
	for _, item := range list {
		if _, ok := table[item]; !ok {
			table[item] = true
			res = append(res, item)
		}
	}
	return res
}
func Contains(list []string, str string) bool {
	for _, item := range list {
		if item == str {
			return true
		}
	}
	return false
}
func Includes(all, subset []string) bool {
	for _, item := range subset {
		if !Contains(all, item) {
			return false
		}
	}
	return true
}
func Union(lists ...[]string) []string {
	var sum int
	for _, l := range lists {
		sum += len(l)
	}
	table := make(map[string]bool, sum)
	res := make([]string, 0, sum)
	for _, list := range lists {
		for _, item := range list {
			if _, ok := table[item]; !ok {
				table[item] = true
				res = append(res, item)
			}
		}
	}
	return res
}