Adding GitHub action to compare benchmarks

The GitHub action runs all the benchmarks for the target branch, and the
compares those values with the benchmarks results for the PR new code.

.github/workflows/echo.yml

@@ -62,3 +62,55 @@ jobs:
         with:
           token:
           fail_ci_if_error: false
+  benchmark:
+    needs: test
+    strategy:
+      matrix:
+        os: [ubuntu-latest]
+        go: [1.15]
+    name: Benchmark comparison ${{ matrix.os }} @ Go ${{ matrix.go }}
+    runs-on: ${{ matrix.os }}
+    steps:
+      - name: Set up Go ${{ matrix.go }}
+        uses: actions/setup-go@v1
+        with:
+          go-version: ${{ matrix.go }}
+
+      - name: Set GOPATH and PATH
+        run: |
+          echo "GOPATH=$(dirname $GITHUB_WORKSPACE)" >> $GITHUB_ENV
+          echo "$(dirname $GITHUB_WORKSPACE)/bin" >> $GITHUB_PATH
+        shell: bash
+
+      - name: Set build variables
+        run: |
+          echo "GOPROXY=https://proxy.golang.org" >> $GITHUB_ENV
+          echo "GO111MODULE=on" >> $GITHUB_ENV
+
+      - name: Checkout Code (Previous)
+        uses: actions/checkout@v2
+        with:
+          ref: ${{ github.base_ref }}
+          path: previous
+
+      - name: Checkout Code (New)
+        uses: actions/checkout@v2
+        with:
+          path: new
+
+      - name: Install Dependencies
+        run: go get -v golang.org/x/perf/cmd/benchstat
+
+      - name: Run Benchmark (Previous)
+        run: |
+          cd previous
+          go test -run="-" -bench=".*" -count=5 ./... > benchmark.txt
+
+      - name: Run Benchmark (New)
+        run: |
+          cd new
+          go test -run="-" -bench=".*" -count=5 ./... > benchmark.txt
+
+      - name: Run Benchstat
+        run: |
+          benchstat previous/benchmark.txt new/benchmark.txt