A simple forward proxy based on nginx for testing purposes. Based on the ngx_http_proxy_connect_module project.

docker build -t nginx-forward-proxy:latest .
docker run --rm -p 3128:3128 nginx-forward-proxy:latest

By default, the proxy binds to port 3128. You can check if it works using curl -x http://localhost:3128 https://privateaim.de.