Mongo 3.6 adds support for using DNS SRV records to configure the initial set of ReplicaSet members instead of providing them in the connection string itself. See: https://docs.mongodb.com/manual/reference/connection-string/#dns-seedlist-connection-format and https://github.com/mongodb/specifications/blob/master/source/initial-dns-seedlist-discovery/initial-dns-seedlist-discovery.rst

It would be great to see support for this in mgo!