Chore: cache go on CI (#1440)

.github/workflows/build-unsigned.yaml

@@ -40,6 +40,14 @@ jobs:
         uses: actions/setup-go@v3
         with:
           go-version: 1.18
+      - uses: actions/cache@v3
+        with:
+          path: |
+            ~/.cache/go-build
+            ~/go/pkg/mod
+          key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
+          restore-keys: |
+            ${{ runner.os }}-go-
       - name: Build
         uses: gradle/gradle-build-action@v2
         with: