Use go mod instead of dep

[phiphi282]

Is your feature request related to a problem? Please describe.
Currently there is a huge vendor folder that should not be needed to be checked out ever time.

Describe the solution you'd like
Instead of dep, go mod should be used in the future.

Additional context
In the past the problem with go libraries was, that there was no versioning.
To make sure that everyone has the same version, the vendor packages must be included in the versioning system.
go mod is still fairly new but I would consider it good enough to be already usable

[phiphi282]

go mod is not a feasible alternative at the moment.
goswagger currently doesn't work with go modules.

This issue will not be worked on until this is fixed in the go-swagger repo.