Why do I get an error when using go1.21?

[SimFG]

The following is my workflow file:

jobs:
  golangci:
    name: lint
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-go@v5
        with:
          go-version: 1.18
      - name: golangci-lint core
        uses: golangci/golangci-lint-action@v6
        with:
          version: latest
          working-directory: ./core
          args: --timeout=5m --out-format=colored-line-number ./...
          skip-cache: true
      - name: golangci-lint server
        uses: golangci/golangci-lint-action@v6
        with:
          version: latest
          working-directory: ./server
          args: --timeout=5m --out-format=colored-line-number ./...
          skip-cache: true

I don't have a go.mod file in my root directory, but there are in the core and server directories. If I use go1.18, github action will work fine, but if I use go1.21, I will get an error that the go file cannot be found.

[ldez]

I guess it's because you have a problem with your go.mod