Issue discovered trying to writing go program to initiate replicaSet trough driver, if server was run with --replicaSet flag (before initiating it in console), driver fails to run any commands/client.Ping() with server selection timeout error.

Connecting to server trough mongo console and doing rs.initiate() + rs.reconfigure() with current connection string e.x. localhost:27017 as members[0].host fixes issue.

Looks like topology just doesn't work with not initialised replicaSet