Feature request: cache the Go build cache

Description:

It doesn't look like setup-go caches the Go build cache, only Go modules and other relevant things.

To speed up subsequent builds, should the go-build directories (OS dependent) also be cached automatically in this action?

Some background available in this blog post https://500.keboola.com/in-depth-of-go-build-cache/

Justification:

I had a job that was taking 3+mins for go test to start, turns out it was because of how long it took to "build" the tests before executing them.

By implementing at least the actions/cache@v4 parts suggested in https://500.keboola.com/in-depth-of-go-build-cache/ that 3mins became single digit seconds.

I suspect this may speed up other peoples builds too.

Example logic:

What I ended up doing in Github Actions in addition to setup-go, differed a little from the blog post (cache based on Go version dynamically being fetched, plus OS + CPU architecture)

      - name: Setup go
        uses: actions/setup-go@v5
        with:
          go-version-file: 'go.mod'

      - name: Get go version for build cache key
        run: |
          echo "GO_VERSION=$(go version | cut -d ' ' -f 3 | cut -d 'o' -f 2)" >> $GITHUB_ENV

      - name: Load Go build cache
        id: load-go-cache
        uses: actions/cache@v4
        with:
          path: |
            ~/.cache/go-build
          key:  ${{ runner.os }}-${{ runner.arch }}-go-${{ env.GO_VERSION }}-somethingunique-${{ hashFiles('**/go.sum') }}
          restore-keys: |
            ${{ runner.os }}-${{ runner.arch }}-go-${{ env.GO_VERSION }}-somethingunique-

Are you willing to submit a PR?

Not right now - I implemented this in my own actions logic for now :)