https://docs.docker.com/toolbox/overview/
What finally worked out for me is based on [https://stackoverflow.com/a/53038417/1323562]:
{ "HostOptions": { ... "EngineOptions": { ... "Env": [ "HTTP_PROXY=%HTTP_PROXY%", "HTTPS_PROXY=%HTTPS_PROXY%", "NO_PROXY=%NO_PROXY%" ], } } }Note: After starting Docker Quickstart Terminal, environment variable will be replaced by actual values.
4. Test it
user@HOST MINGW64 /c/Program Files/Docker Toolbox$ docker run hello-worldUnable to find image 'hello-world:latest' locallylatest: Pulling from library/hello-world1b930d010525: Pull completeDigest: sha256:41a65640635299bab090f783209c1e3a3f11934cf7756b09cb2f1e02147c6ed8Status: Downloaded newer image for hello-world:latestHello from Docker!This message shows that your installation appears to be working correctly.