Add set util

internal/utils/set.go

@@ -0,0 +1,33 @@
+package utils
+
+var exists = struct{}{}
+
+type set struct {
+	m map[string]struct{}
+}
+
+func NewSet() *set {
+	s := &set{}
+	s.m = make(map[string]struct{})
+	return s
+}
+
+func (s *set) Add(value string) {
+	s.m[value] = exists
+}
+
+func (s *set) Remove(value string) {
+	delete(s.m, value)
+}
+
+func (s *set) List() (list []string) {
+	for key, _ := range s.m {
+		list = append(list, key)
+	}
+	return
+}
+
+func (s *set) Contains(value string) bool {
+	_, c := s.m[value]
+	return c
+}