When flying from Russia to Goa, the time of day you decide to fly out makes little to no difference towards the overall price you’ll pay on tickets.
These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Belaya Gora Airport to Vasco da Gama Goa Intl Airport flight would often be abbreviated as a BGN to GOI flight. While you’re still figuring out your travel plans, it’s not a bad idea to learn the names and codes of other airports around these areas: Bogorodskoye Airport (BQG), Batagay Airport (BQJ), Blagoveschensk Airport (BQS), Bratsk Airport (BTK), Bovanenkovo Airport (BVJ).