It looks like a timeout while trying to download the script from https://raw.githubusercontent.com/home-assistant/hassio-build/master/install/hassio_install
You should also be able to get there with a browser and possibly redirect to a file. The curl command gets that script & the end part silently runs the script using the bash shell.
My searching has found that it is actually an error with docker not having access to the internet but after trying multiple ways of fixing this, I am not having any luck. I am not running any kind of proxy and have resolv.conf setup with google’s nameservers