Add documentation on how to update dependencies

[kevinburke]

I've been trying and failing to update dependencies by running go get newdep@version with GO111MODULE=on set in my environment.

It would be helpful to have instructions on the correct way to do so. It seems like a lot of stuff is happening that is not strictly necessary to get a single version to update.

[mcuadros]

Hi @kevinburke I just update all the dependencies, but its weird a I didn't have any problem about it. We don't have any special method or setup. Maybe is something in your side?