CI: trigger less often

.github/workflows/go.yml

@@ -1,13 +1,19 @@
 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:
@@ -16,12 +22,13 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v4
         with:
-        go-version: '1.20'
+          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