Fix dependency management in the project

[thegrumpylion]

Currently QMSTR uses dep for dependency management. We should either:

• Use dep properly by commiting Gopkg.lock to the repo.
• Migrate to go mod

[thegrumpylion]

After some back and forth with Markus, the choice is obvious. Go mod is the way to go (no pun intended) since is build into the whole go tooling, and many more.

[thegrumpylion]

The steps for this should be simple

go mod init
go mod tidy

But this fails with

...
go: github.com/Sirupsen/logrus@v1.3.0: parsing go.mod: unexpected module path "github.com/sirupsen/logrus"
go: error loading module requirements

The reason is that it pulls an old version of docker that depends on a a path with upercase letter. After digging around it seems this will not be an issue with go 1.12

Even if you try manually pulling docker by the means of

go mod init
go get github.com/docker/docker@v17.05.0-ce
go mod tidy

it still fails with the same issue. The reason being that v17.05.0-ce (which is the latest?) is relatively old (2017-05-04)

A solution to this is pulling a version i found in this golang/go#26208 which is from 2018-04-22

go mod init
go get github.com/docker/docker@v0.0.0-20180422163414-57142e89befe
go mod tidy

So this got me thinking that versions from that date an on should also work. So i tried with pulling docker master and it worked as expected.

go mod init
go get github.com/docker/docker@master
go mod tidy

So the question becomes on which commit of the docker repository do we want to depend on? We can try building with current master and if everything works we can stick with that until we find a better version to update to.

@hemarkus any input?

[thegrumpylion]

Let's wait for golang 1.12 to be out and look into this again

[hemarkus]

Find task for migration here QMSTR/qmstr#262