Error in vendoring of third party library(mgo.v2)

I am trying to have a local copy of current code base of mgo.v2. https://gopkg.in/mgo.v2 says to install using go get gopkg.in/mgo.v2. I forked it from https://github.com/go-mgo/mgo/tree/v2 and trying to install it from go get forked repo from git but it changes the package structure(changes from /src/gopkg.in --> /src/github.com) and it fails saying

src/github.com/eateshk/mgo.v2/error.go:4: "ERROR: the correct import path is gopkg.in/mgo.v2 ... " evaluated but not used

I understand the error, but what's the solution for this ?

This is a common problem when forking go packages. Canonical or "vanity" imports require the code to live in the specified path or they won't compile. The only solution is to remove the // import "gopkg.in/whatever" comment that exists somewhere.

There are other problems with your approach as well. imports within their repository will resolve back to the original repo and cause all kinds of confusion unless you rewrite them.

Rather, I suggest an alternate approach. The only place this can live on disk without causing problems is $GOPATH/src/gopkg.in/mgo.v2. Anything else will cause problems. So:

go get gopkg.in/mgo.v2
cd $GOPATH/src/gopkg.in/mgo.v2
git remote add mine your_git_fork

Now you can pull upstream changes from origin and push your changes to mine. It feels a bit odd, but it really is the only way to work from a fork without causing tons of extra pain by rewriting things.