Update build and CI images to Go 1.13
Go 1.13 will be the new version for all Go applications within GitLab (see omnibus-gitlab#5179 (closed)). We should strive for consistency and use this version for all our build test and build processes.
Go 1.13 will be the new version for all Go applications within GitLab (see omnibus-gitlab#5179 (closed)). We should strive for consistency and use this version for all our build test and build processes.