Add gofmt Github action

This runs gofmt and make sure no files need to be reformatted.

.github/workflows/gofmt.yml

@@ -0,0 +1,29 @@
+name: gofmt
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+jobs:
+
+  gofmt:
+    name: Run gofmt
+    runs-on: ubuntu-latest
+    steps:
+
+    - name: Set up Go 1.13
+      uses: actions/setup-go@v1
+      with:
+        go-version: 1.13
+      id: go
+
+    - name: Check out code into the Go module directory
+      uses: actions/checkout@v1
+
+    - name: gofmt
+      run: |
+        if [ "$(find . -iname '*.go' | xargs gofmt -l)" ]
+        then
+          find . -iname '*.go' | xargs gofmt -d
+          exit 1
+        fi