Upgrade to the latest version of the setup-go github action

[AntonNguyen]

The github action pipeline is currently broken, giving us the following error:

Run actions/setup-go@v2-beta
Setup go  version spec 1.14
Error: Unable to process command '::set-env name=GOROOT::/opt/hostedtoolcache/go/1.14.12/x64' successfully.
Error: The `set-env` command is disabled. Please upgrade to using Environment Files or opt into unsecure command execution by setting the `ACTIONS_ALLOW_UNSECURE_COMMANDS` environment variable to `true`. For more information see: https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/

The beta version utilizes the deprecated set-env and add-path commands. In the 2.1.3 release, they've introduced a fix (actions/setup-go#76) by upgrading the core library. More details can be found at https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/

Sample faling build: https://github.com/go-kit/kit/pull/1013/checks?check_run_id=1453805584

[peterbourgon]

Agh!! Thank you!!