Support Golang v1.14 and v1.15 in CI
Changes Gitaly's test and build versions of Golang from v1.13/v1.14 -> v1.14/v1.15. It also fixes tests that broke from the new version.
Closes #3036 (closed) & #3313
Edited by Paul Okstad (ex-GitLab)
Changes Gitaly's test and build versions of Golang from v1.13/v1.14 -> v1.14/v1.15. It also fixes tests that broke from the new version.
Closes #3036 (closed) & #3313