How to fix "set-output" when reading nvmrc from the GitHub Actions?

You may be getting the issue "The set-output command is deprecated and will be disabled soon. Please upgrade to using Environment Files." from your Github workflow.

Screenshot showing the 'set-output' issue from the Github workflows

Few months ago, I choose to update some of my Github workflows to read from my .nvmrc file instead of manually specifying my node version.

.github/workflows/production.yml

on: push

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - name: Detect Node version
        run: echo ::set-output name=NODE_VERSION::$(cat .nvmrc)
        id: nvmrc

      - name: Use Node.js ${{ steps.nvmrc.outputs.NODE_VERSION }}
        uses: actions/setup-node@v3
        with:
          node-version: ${{ steps.nvmrc.outputs.NODE_VERSION }}

But since October 2022 and the runner version 2.298.2, Github shows a warning regarding a future depreciation of the set-output command.

After few trials, I figured out how to update using the $GITHUB_OUTPUT instead:

.github/workflows/update-production.yml

on: push

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - name: Detect Node version
        run: echo "NODE_VERSION=$(cat .nvmrc)" >> $GITHUB_OUTPUT
        id: nvmrc
        # shell: bash (to be added if you use composite actions)

      - name: Use Node.js ${{ steps.nvmrc.outputs.NODE_VERSION }}
        uses: actions/setup-node@v3
        with:
          node-version: '${{ steps.nvmrc.outputs.NODE_VERSION }}'

And "voilà", the warning should have disappeared and you should see the number of the version right after Use Node.js XXXX in your workflow.