[actions] add caching of benchmark results

Author: capcom6

.github/workflows/go.yml

@@ -97,6 +97,14 @@ jobs:
       - name: Run benchmarks
         run: go test -bench=. -benchmem ./... | tee benchmark.txt
 
+      # step 5: download previous benchmark result from cache (if exists)
+      - name: Download previous benchmark data
+        uses: actions/cache@v4
+        with:
+          path: ./cache
+          key: ${{ runner.os }}-benchmark
+
+      # step 6: upload benchmark
       - name: Upload benchmark results
         uses: benchmark-action/github-action-benchmark@v1
         with: