Update to Go 1.12

[dpordomingo]

Since Go 1.12 is already there and both Go v1.11 and Go v1.12 supports Go Modules, we could also update .travis to v1.12.x and migrate from dep to go mod

[smacker]

I would wait until we update go-conventions: https://github.com/src-d/guide/blob/master/engineering/conventions/go.md

[carlosms]

I'm going to edit this issue to drop go mod and focus on go 1.12. We need to check travis, and the base docker images.

[dpordomingo]

but then we need another issue for go mod migration

[carlosms]

But we can open it when the conventions guidelines are updated, don't you think?

[dpordomingo]

I understood that it was a thing to do from a message from @smola on company Slack channels.

[carlosms]

Alright, then feel free to open a new issue for go mod. I guess we may have things to discuss (vendor vs no vendor for instance), while the go 1.12 is straightforward and should not depend on the go mod discussion.

[smacker]

agree with Carlos on that. There is also a question about go mod tidy for example.

[dpordomingo]

When I opened this issue I considered it would be like an umbrella for such different tasks and discussions... but ok, here is the new issue.