Network timed out while trying to connect to https://index.docker.io
I had the same problem this morning and the following fixed it for me:
$ docker-machine restart default # Restart the environment$ eval $(docker-machine env default) # Refresh your environment settingsIt appears that this is due to the Docker virtual machine getting itself into a strange state. There is an open github issue here
I installed Docker without the Toolbox on Windows 10, so the version that requires Hyper-V to be enabled.
For Docker version 1.12 I had to go into the taskbar, right click the Docker Icon, select Settings -> Network and set the DNS Server to fixed, so that is uses Google's DNS server at 8.8.8.8.
Once that setting was changed, it finally worked.
The simpler solution is to add the following entry in /etc/default/docker file
export http_proxy="http://HOST:PORT/"
and restart the docker service
service docker restart