Go package management is a mess right now. gopkg.in was a band-aid and worked well if dependencies were on the master branch or followed gopkg.in convention. The problem is and has always been how do you lock down to a specific commit or tag? That's where glide shines.
Install glide
If you are not using glide in your project
cd $GOPATH/src
# remove dir if it exists
# rm -rf github.com/bcmi-labs/dat
git clone -b v1 https://github.com/mgutz/dat github.com/bcmi-labs/dat
cd github.com/bcmi-labs/dat
glide installIf you are already using glide for your project
glide get github.com/bcmi-labs/dat