Use network proxy environment settings for "sudo" user on Linux

the trick is to add enviroment variables to sudoers config:

sudo nano /etc/sudoers

add these lines:

Defaults env_keep +="http_proxy"
Defaults env_keep +="https_proxy"

from ArchLinux wiki https://wiki.archlinux.org/index.php/Sudo#Environment_variables_.28Outdated.3F.29