You need go version 1.7x, so it may be in stable…I went with 6.0 -current

pkg_add go
cd $HOME
mkdir -p godev/src
cd godev/src
git clone https://github.com/cloudfoundry/cli.git
cd cli
go get .
go install

OR, even easier:

Create a new workspace, set export GOPATH=</path/to/workspace>, then cd $GOPATH and go get code.cloudfoundry.org/cli and it should automatically pull down cli,
dependencies, and build it into $GOPATH/bin.