Add cache to unit tests workflow

.github/workflows/unit_tests.yaml

@@ -10,6 +10,14 @@ jobs:
       uses: actions/setup-go@v2
       with:
         go-version: 1.17
+    - uses: actions/cache@v2
+      with:
+        path: |
+          ~/go/pkg/mod
+          ~/.cache/go-build
+        key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
+        restore-keys: |
+          ${{ runner.os }}-go-
     - name: Run tests
       run: go test -v -covermode=count -coverprofile=coverage.out
     - name: Convert coverage to lcov