Report test coverage in GitHub workflow

.github/workflows/go.yml

@@ -7,6 +7,8 @@ jobs:
         go-version: [1.11.x, 1.12.x, 1.13.x]
         platform: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.platform }}
+    env:
+      GO111MODULE: "on"
     steps:
 
     - name: Install Go
@@ -18,16 +20,19 @@ jobs:
       uses: actions/checkout@v1
 
     - name: Download Go modules
-      env:
-        GO111MODULE: "on"
       run: go mod download
 
     - name: Build
-      env:
-        GO111MODULE: "on"
       run: go build -v ./...
 
     - name: Test
-      env:
-        GO111MODULE: "on"
       run: go test ./...
+
+    - name: Coverage
+      env:
+        COVERALLS_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      run: |
+        go test -race -covermode atomic -coverprofile=profile.cov ./...
+        GO111MODULE=off go get github.com/mattn/goveralls
+        $(go env GOPATH)/bin/goveralls -coverprofile=profile.cov -service=github
+      if: matrix.go-version == '1.13.x' && matrix.platform == 'ubuntu-latest'