Add Go version matrix

.gitlab-ci.yml

@@ -44,12 +44,29 @@ rspec:ruby2.1:
   except:
     - tags
 
-go:
-  # Image taken from gitlab-ce@59f81b4ff8
-  image: "dev.gitlab.org:5005/gitlab/gitlab-build-images:ruby-2.3.3-golang-1.8-git-2.7-phantomjs-2.1-node-7.1"
+.go: &go_definition
+  before_script:
+  - apt-get update -qq && apt-get install -y ruby
+  - ruby -v
   script:
     - go version
     - which go
     - bin/compile
     - support/go-test
     - support/go-format check
+
+go:1.8:
+  <<: *go_definition
+  image: golang:1.8
+
+go:1.7:
+  <<: *go_definition
+  image: golang:1.7
+
+go:1.6:
+  <<: *go_definition
+  image: golang:1.6
+
+go:1.5:
+  <<: *go_definition
+  image: golang:1.5