Upgrade Go Guide

This procedure describes how to upgrade Golang for the cf CLI project.

Phase 1: Confirm that upgrade works locally:

Read the release notes: https://golang.org/doc/devel/release.html
Update install-ubuntu.sh's GoLang version and rerun on local workstation.
- Update the GOROOT variable in 0000-paths.bash
- This may require rerunning the GoUpdateBinaries in vim on all the workstations after GoLang was updated.
Run the unit and integration tests. Fix any tests that fail and commit changes.
Run go get -u golang.org/x/<pkg> for golang.org/x/ packages we directly depend on
- Make sure to rerun the unit and integration tests. (https://github.com/cloudfoundry/cli/blob/master/.github/CONTRIBUTING.md#development-environment-setup).
Individually pause all the jobs in the cli group in Concourse.
Push changes made to cf cli repo.

Update and push the ci/cli-base/Dockerfile image's FROM golang:<major>.<minor> . Then run the create-cli-base-image Concourse Job.
Upgrade GoLang on the OSX Worker: Run brew update and brew upgrade golang. Connection instructions here
Upgrade GoLang on the Windows worker(s) by updating this pipeline
Update TARGET_GO_VERSION in cli-ci with the new version #
Refly the pipelines with ci/bin/reconfigure-pipelines, ci/bin/reconfigure-v7-pipelines and ci/bin/reconfigure-v8-pipelines
Starting from the unit tests, unpause each job - waiting for the job to pass with the latest version of GoLang before unpausing the subsequent job.
Update the version number in the [developer guide]
Commit and Push the install-ubuntu.sh version update, and rerun it on all the workstations.