Please use the following steps to build and install Delve on FreeBSD.
There are two ways to install on FreeBSD. First is the standard go get method:
go get -u github.com/go-delve/delve/cmd/dlv
Alternatively make sure $GOPATH is set (e.g. as ~/.go) and:
$ git clone https://github.com/go-delve/delve.git $GOPATH/src/github.com/go-delve/delve
$ cd $GOPATH/src/github.com/go-delve/delve
$ gmake install
Note: If you are using Go 1.5 you must set GO15VENDOREXPERIMENT=1 before continuing. The GO15VENDOREXPERIMENT env var simply opts into the Go 1.5 Vendor Experiment.