Update deps

[Felixoid]

Not sure if we need vendor directory, but it improves the docker buildings significantly

[Hipska]

I heard that this was the old way of golang to manage modules. I think we can get rid of it when using current golang versions.

[Felixoid]

it's officially supported by go mod vendor + -mod=vendor flag.

• as said, it reduces docker build time very much

I don't say we must keep it, but it's the info to consider