ci: replace setup-go with custom action to avoid cache error and test pre-release go

.github/workflows/fmt.yml

@@ -13,9 +13,9 @@ jobs:
       - uses: actions/checkout@v4
 
       - name: Set up Go
-        uses: actions/setup-go@v5
+        uses: ./.github/actions/setup-go
         with:
-          go-version: '1.23'
+          go-version: '1.23.6'
 
       - name: Check formatting
         run: |