windows CI testing

.circleci/config.yml

 version: 2.1
 orbs:
   ci-go: ipfs/ci-go@0.2.1
+  win: circleci/windows@2.4.0
+
+jobs:
+  "windows-test":
+    executor: win/default
+    steps:
+      - checkout
+      - run:
+          name: "Go test"
+          command: go test .
 
 workflows:
   version: 2
@@ -9,3 +19,4 @@ workflows:
       - ci-go/build
       - ci-go/lint
       - ci-go/test
+      - windows-test