fix the action error with no go.sum file

Signed-off-by: zhzhuang-zju <m17799853869@163.com>

.github/workflows/ci.yml

@@ -34,20 +34,13 @@ jobs:
   codegen:
     name: codegen
     runs-on: ubuntu-22.04
-    env:
-      GOPATH: ${{ github.workspace }}
-    defaults:
-      run:
-        working-directory: ${{ env.GOPATH }}/src/github.com/karmada-io/karmada
     steps:
       - name: checkout code
         uses: actions/checkout@v4
-        with:
-          path: ${{ env.GOPATH }}/src/github.com/karmada-io/karmada
       - name: install Go
         uses: actions/setup-go@v5
         with:
-          go-version-file: ${{ env.GOPATH }}/src/github.com/karmada-io/karmada/go.mod
+          go-version-file: go.mod
       - name: Install Protoc
         uses: arduino/setup-protoc@v3
         with: