how to connect from docker container to localhost
host.docker.internal
Solution
% curl -i -X POST http://host.docker.internal:8000/webhook -d a=b
https://stackoverflow.com/a/63112795/1399891
https://docs.docker.com/docker-for-windows/networking/
host.docker.internal
% curl -i -X POST http://host.docker.internal:8000/webhook -d a=b