add format check job in CI

.circleci/config.yml

@@ -1,14 +1,29 @@
-version: 2
-jobs:
-  build:
-    docker:
-    - image: circleci/golang:1.11.1
-    working_directory: /go/src/kubeedge
-    steps:
-    - checkout
-    - run: make
-workflows:
-  version: 2
-  workflow:
-    jobs:
-    - build
+version: 2
+
+# Docker environment.
+defaults: &defaults
+  working_directory: /go/src/kubeedge
+  docker:
+  - image: circleci/golang:1.11.1
+
+jobs:
+  build:
+    <<: *defaults
+    steps:
+    - checkout
+    - run: make
+
+  format:
+    <<: *defaults
+    steps:
+    - checkout
+    - run:
+        name: Check Format
+        command: /go/src/kubeedge/hack/gofmt.sh -v
+
+workflows:
+  version: 2
+  workflow:
+    jobs:
+    - format
+    - build