move StringSet to utils package

irc/utils/types.go

@@ -0,0 +1,17 @@
+// Copyright (c) 2020 Shivaram Lingamneni
+// released under the MIT license
+
+package utils
+
+type empty struct{}
+
+type StringSet map[string]empty
+
+func (s StringSet) Has(str string) bool {
+	_, ok := s[str]
+	return ok
+}
+
+func (s StringSet) Add(str string) {
+	s[str] = empty{}
+}