Awesome

killswitch

VPN kill switch for macOS (Mac OS X >= 10.6), it will block outgoing traffic when VPN connection fails or crashes.

https://vpn-kill-switch.com/

Usage:

$ killswitch

To enable:

$ sudo killswitch -e

To disable:

$ sudo killswitch -d

Compile from source

Setup go environment https://golang.org/doc/install

For example using $HOME/go for your workspace

$ export GOPATH=$HOME/go

Clone project into that directory:

$ go get github.com/vpn-kill-switch/killswitch

Build by just typing make:

$ cd $GOPATH/src/github.com/vpn-kill-switch/killswitch
$ make