This post is a combination of information available elsewhere (links are included) and can be used to get you’re own offline buildpack on Cloud Foundry.

Prerequisites

install go (https://ahmadawais.com/install-go-lang-on-macos-with-homebrew/)

Dotnet-core buildpack

Instructions on https://github.com/cloudfoundry/dotnet-core-buildpack/tree/v2.0.1

cd ~/workspace
git clone https://github.com/cloudfoundry/dotnet-core-buildpack
cd dotnet-core-buildpack
git checkout v2.0.1 #I'm on v2.0.1, you may need another version
export GOPATH="${HOME}/.go"
export GOROOT="$(brew --prefix golang)/libexec"
export PATH="$PATH:${GOPATH}/bin:${GOROOT}/bin"
source .envrc
(cd src/*/vendor/github.com/cloudfoundry/libbuildpack/packager/buildpack-packager && go install)
buildpack-packager --cached
cf create-buildpack offline-dotnet-core dotnet-core_buildpack-cached-v2.0.1.zip 1

Warning! buildpack is 841MB.

Now you can use you’re offline buildpack with the -b parameter:

cf push core -b offline-dotnet-core