CI: trigger less often

.github/workflows/go.yml

@@ -1,27 +1,34 @@
 name: Go
 
 on:
+  workflow_dispatch:
   push:
-    branches: [ "main" ]
+    branches: ["main"]
+    paths:
+      - main.go
+      - .github/workflows/go.yml
   pull_request:
-    branches: [ "main" ]
+    branches: ["main"]
+    paths:
+      - main.go
+      - .github/workflows/go.yml
 
 jobs:
-
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
+      - uses: actions/checkout@v4
 
-    - name: Set up Go
-      uses: actions/setup-go@v4
-      with:
-        go-version: '1.20'
-
-    - name: Build
-      run: go build -v ./.
-
-    - name: Cache
-      uses: actions/cache@v3.3.2
+      - name: Set up Go
+        uses: actions/setup-go@v4
+        with:
+          go-version: "1.20"
 
+      - name: Build
+        run: go build -v ./.
 
+      - name: Cache
+        uses: actions/cache@v3.3.2
+        with:
+          path: go-grep-cache
+          key: ${{ runner.os }}-go-grep-cache