Use ResizeOptsBuilder, not ResizeOpts.
diff --git a/openstack/compute/v2/servers/requests.go b/openstack/compute/v2/servers/requests.go
index 26a8525..c6eca11 100644
--- a/openstack/compute/v2/servers/requests.go
+++ b/openstack/compute/v2/servers/requests.go
@@ -485,7 +485,7 @@
// While in this state, you can explore the use of the new server's configuration.
// If you like it, call ConfirmResize() to commit the resize permanently.
// Otherwise, call RevertResize() to restore the old configuration.
-func Resize(client *gophercloud.ServiceClient, id string, opts ResizeOpts) ActionResult {
+func Resize(client *gophercloud.ServiceClient, id string, opts ResizeOptsBuilder) ActionResult {
var res ActionResult
reqBody, err := opts.ToServerResizeMap()
if err != nil {