ci: cache + dependabot (#5)

* ci: share go mod cache for better efficiency
* dependabot

.github/dependabot.yaml

@@ -0,0 +1,14 @@
+version: 2
+updates:
+  - package-ecosystem: "gomod"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    reviewers:
+      - "firehydrant/open-source-maintainers"
+  - package-ecosystem: "gomod"
+    directory: "/_tools"
+    schedule:
+      interval: "daily"
+    reviewers:
+      - "firehydrant/open-source-maintainers"

.github/workflows/build-test.yaml

@@ -13,8 +13,31 @@ permissions:
   checks: write
 
 jobs:
+  mod:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: 1.22.x
+          cache-dependency-path: |
+             ./go.sum
+             _tools/go.sum
+
+      - name: Go version
+        run: go version
+
+      - name: Go mod tidy
+        run: |
+          go mod tidy
+          cd _tools && go mod tidy && cd ..
+          git diff --exit-code
+
   test:
     runs-on: ubuntu-latest
+    needs: [mod]
     steps:
       - uses: actions/checkout@v4
 
@@ -43,6 +66,7 @@ jobs:
 
   lint:
     runs-on: ubuntu-latest
+    needs: [mod]
     steps:
       - uses: actions/checkout@v4
 
@@ -68,6 +92,7 @@ jobs:
 
   build:
     runs-on: ubuntu-latest
+    needs: [mod]
     steps:
       - uses: actions/checkout@v4