Hello, new feature in octavia loadbalancer (additional_vips) are not implemented in gophercloud.
Taking the point.

https://github.com/gophercloud/gophercloud/blob/master/openstack/loadbalancer/v2/loadbalancers/results.go#L16
https://github.com/gophercloud/gophercloud/blob/master/openstack/loadbalancer/v2/loadbalancers/requests.go#L80

https://docs.openstack.org/api-ref/load-balancer/v2/?expanded=show-load-balancer-details-detail#show-load-balancer-details

New in version 2.26