If you want to shorten these, you can just import that namespace:
Net::HTTP.start(...)
include Net
# HTTP.start(...)
Be careful when you import aggressively as it might cause conflict within your class if you get carried away.
An alternative is to create aliases:
HTTP = Net::HTTP
Get = Net::HTTP::Get
The "correct" way is to just spell it out and not get too flustered by that. A typical Ruby program will bury this sort of low-level behavior beneath an abstraction layer so it's rarely a big deal.