The official athens Docker image ignore --add-host parameter

Describe the bug
When running the gomods/athens image from the hub, it ignores the --add-host option.
It seems it comes from this bug : docker-library/docker#82
So I guess we should add some nsswitch.conf?
My use case was to test vanity urls hosted internally. And for testing, I ran a https://github.com/GoogleCloudPlatform/govanityurls on my host, so I needed a way for it to be accessed from the athens container.

Error Message

To Reproduce
Have a service like https://github.com/GoogleCloudPlatform/govanityurls running on your machine on port :80. It should be configured to point to some github repository.

docker run -d --name athens --add-host mydomain.com:172.17.0.1 -v /home/dolanor/var/lib/athens:/var/lib/athens -e ATHENS_DISK_STORAGE_ROOT=/var/lib/athens -e ATHENS_STORAGE_TYPE=disk gomods/athens:latest
export GOPROXY=http://`docker inspect -f "{{ .NetworkSettings.IPAddress}}"`:3000 athens
export GO111MODULE=on
go get -v mydomain.com/mypkg

Expected behavior
The athens proxy container should try to go on mydomain.com that is running on the host and from there go to a private repo on github

Environment (please complete the following information):

• OS: Linux 64bit
• Go version : Go 1.12.5
• Proxy version : 2019-05-09-20:44:12-UTC
• Storage (fs/mongodb/s3 etc.) : disk

Start by reproducing the documented docker run with --add-host and inspect how the official gomods/athens image handles name resolution. Done means a container started this way can resolve mydomain.com and fetch the configured vanity URL through the host service.