Update Go version for .gitlab-ci.yml

4 jobs for master in 6 minutes (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #16418
android

00:06:00

passed #16421
debian-testing

00:02:47

passed #16419
go-1.13

00:01:38

passed #16420
go-1.14

00:01:38