Upgrade to Go 1.13

Overview

We are running go1.10 when we merge !1615 (merged) which is still on a version that is deprecated and we should upgrade to the latest version of Go which is 1.13.

Proposal

• Upgrade the CI to start using go 1.13
• Migrate to modules in a separate issue maybe?

Bugs that will be fixed

• KeepAlive for docker-machine executor on GCP which results in missing output ➡ gitlab#34951 (comment 244354981)

Issues blocked by this

• #4874 (closed)