code: func (s *Session) DB(name string) *Database {
  	if name == "" {
  		name = s.defaultdb
  	}
  	return &Database{s, name}
  }
docs: // DB returns a value representing the named database. If name
  // is empty, the database name provided in the dialed URL is
  // used instead. If that is also empty, "test" is used as a
  // fallback in a way equivalent to the mongo shell.
  //
  // Creating this value is a very lightweight operation, and
  // involves no network communication.