I hate to always post links to Greg Egan, but he's sort of the XKCD of SciFi - if there's an out there concept, he's usually written a book about it. In this case Incandescence:
Top review has the best summary: "Egan's story is set in the galactic core, inhabited by a race known as the Aloof, because they seem almost indifferent to any attempts at communication from the Amalgam, the loose network of civilizations that inhabit the rest of the galaxy. However, they do allow thrill-seeking members of the Amalgam to enter their transportation network, digitizing themselves for transmission at the speed of light across the galactic core, instead of the long way around it."
https://www.amazon.com/dp/B0070YQOHW
Top review has the best summary: "Egan's story is set in the galactic core, inhabited by a race known as the Aloof, because they seem almost indifferent to any attempts at communication from the Amalgam, the loose network of civilizations that inhabit the rest of the galaxy. However, they do allow thrill-seeking members of the Amalgam to enter their transportation network, digitizing themselves for transmission at the speed of light across the galactic core, instead of the long way around it."