fix up pkg.go.dev

go.mod

@@ -0,0 +1,22 @@
+//
+// Copyright 2020-2022 Sean C Foley
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+module github.com/seancfoley/ipaddress-go
+
+go 1.12
+
+require github.com/seancfoley/bintree v1.1.0
+