docker-registry-proxy behind another proxy

[lcorsini]

Hi, I'm currently using docker-registry-proxy to reach a gitlab registry from a k8s cluster using docker-engine.
it works fine, but being inside a corporate network means that I cannot reach dockerhub or quay or gcr freely without passing through another proxy, I was thinking, is there a way to specify to use a proxy to reach those destinations inside docker-registry-proxy while keeping direct connection to gitlab?