func (s *Int16) Add(num int16) *Int16 {
	if s.nodeMap == nil {
		s.nodeMap = make(map[int16]struct{})
	}
	_, ok := s.nodeMap[num]
	if !ok {
		s.nodeMap[num] = struct{}{}
	}
	return s
}
Add an item
package set
type Int16 struct {
	nodeMap map[int16]struct{}
}
func NewInt16(nums []int16) *Int16 {
	s := &Int16{}
	for _, num := range nums {
		s.Add(num)
	}
	return s
}