Docker not exposing port on mojave mac
Most likely the port is published on the VM and you are trying to connect to your laptop's IP and not seeing it. Newer versions of docker that use xhyve include some networking tricks to publish the port all the way to your laptop, but docker-machine with VirtualBox does not do this.

You can lookup the IP of your VM with docker-machine ls or see it in the variable echo $DOCKER_HOST and connect to port 8000 on that IP to reach your application.