I don't know about the Go part, but on the db side i have no doubt: go with PostgreSQL.<p>I advise you in ANY case to read about both ... more ... and more in depth.<p>Mongo is nice but i can't see an use for it as a proper DB, it is useful from other perspectives (similar argument to why chose nodejs or not), but given the position i assume you are in, as single man army, you need to know what you are doing, and skipping the data part is a big mistake, you have to know what is your data and how to structure it, you can't let your models define it ... or you could, and grant yourself maintenance work forever ...<p>PostgreSQL on the other hand is one of the best, if not the best database, and if you are worrying about performance, you are worrying about the wrong things, and from the wrong angle, and still Postgre have amazing performance if you know what you are doing.<p>I would consider using mongo for only two reasons: just for fun, or because i need to ship in zero time, and in the latter i would think twice and go with Postgre anyway ...<p>PS. I might have been a bit trolly on the mongo side, but seriously give Postgres a shot, every minute you spend on it is worth more than the specific knowledge you gain!