func (s Int64) Insert(items ...int64) {
	for _, item := range items {
		s[item] = Empty{}
	}
}
Insert adds items to the set.
package sets
import (
	"reflect"
	"sort"
)
type Int64 map[int64]Empty
func NewInt64(items ...int64) Int64 {
	ss := Int64{}
	ss.Insert(items...)
	return ss
}
func Int64KeySet(theMap interface{}) Int64 {
	v := reflect.ValueOf(theMap)
	ret := Int64{}
	for _, keyValue := range v.MapKeys() {
		ret.Insert(keyValue.Interface().(int64))
	}
	return ret
}