Go version needs to be upgraded to 1.14.12 or 1.15.5

@ankelly reported a security issue where we need to upgrade to newer golang version.

Please see https://gitlab.com/gitlab-org/gitlab-elasticsearch-indexer/-/issues/70 for the context.

It seems to me that we are using golang1.14. So we need to upgrade to 1.14.12 or 1.15.5

• https://github.com/golang/go/milestone/182?closed=1
• https://github.com/golang/go/milestone/183?closed=1