code: func (ln *Listener) Listen(channels ...string) error {
  	// Always append channels so DB.Listen works correctly.
  	ln.channels = appendIfNotExists(ln.channels, channels...)
  
  	cn, err := ln.conn()
  	if err != nil {
  		return err
  	}
  
  	err = ln.listen(cn, channels...)
  	if err != nil {
  		ln.releaseConn(cn, err, false)
  		return err
  	}
  
  	return nil
  }
docs: // Listen starts listening for notifications on channels.