The framework 'Microsoft.NETCore.App', version '3.1.0' was not found in GitHub Actions

Question

when i push the code to github, and create the file workflow\dotnet.yml.

name: dotnet package

on: [push]

jobs:
  build:

    runs-on: ubuntu-latest
    strategy:
      matrix:
        dotnet-version: ['5.0.x' ]

    steps:
      - uses: actions/checkout@v3
      - name: Setup .NET Core SDK ${{ matrix.dotnet-version }}
        uses: actions/setup-dotnet@v2
        with:
          dotnet-version: ${{ matrix.dotnet-version }}
      - name: Install dependencies
        run: dotnet restore
      - name: Build
        run: dotnet build --configuration Release --no-restore
      - name: Test
        run: dotnet test --no-restore --verbosity normal

In the Actions output, the following error is shown.

The framework 'Microsoft.NETCore.App', version '3.1.0' was not found.
The following frameworks were found: 5.0.17 at [/home/runner/.dotnet/shared/Microsoft.NETCore.App]

Followed the link, and installed the frameworks, but it still errors. Can anyone provide help with this?