# go version
go version go1.9.2 linux/amd64

# go env
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/actionmystique/src/GO-Packages"
GORACE=""
GOROOT="/usr/lib/go"
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build413906626=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"

# go get github.com/ncw/rclone
...
# cd github.com/ncw/rclone
# git checkout v1.39
Note: checking out 'v1.39'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

  git checkout -b <new-branch-name>

HEAD is now at f34a9116... Version v1.39

# go get -u -v github.com/ncw/rclone
github.com/ncw/rclone (download)
cd /home/actionmystique/src/GO-Packages/src/github.com/ncw/rclone; git pull --ff-only
You are not currently on a branch.
Please specify which branch you want to merge with.
See git-pull(1) for details.

    git pull <remote> <branch>

package github.com/ncw/rclone: exit status 1

# go get <git_package> <git_tag>

# git checkout <git_tag>
# go get -u <git_package>