This made me wonder what the oldest go-link (from inside Google) discoverable on the public internet is. The earliest I've found is from Nov 2009: https://github.com/google/closure-library/blame/11ed104958a2.... (The second closest I've found in another repo is in RE2 from Mar 2010, https://github.com/google/re2/blame/954656f47fe8fb505d4818da... - and yes, both of these existed prior to the listed date, but I'm going off associated timestamps.)

(Fun fact: go-links are so critical to Google ops, that they're expected to be accessible in a "everything is down" scenario.)