curl --request PATCH \
  --url https://api.gcore.com/cloud/v1/floatingips/{project_id}/{region_id}/{floating_ip_id} \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: application/json' \
  --data '{
  "tags": {
    "my-tag": "my-tag-value",
    "my-tag-to-remove": null
  }
}'

{
  "created_at": "2019-06-13T13:58:12+0000",
  "creator_task_id": "d1e1500b-e2be-40aa-9a4b-cc493fa1af30",
  "fixed_ip_address": "192.168.10.15",
  "floating_ip_address": "172.24.4.34",
  "id": "c64e5db1-5f1f-43ec-a8d9-5090df85b82d",
  "port_id": "ee2402d0-f0cd-4503-9b75-69be1d11c5f1",
  "project_id": 1337,
  "region": "Luxembourg 1",
  "region_id": 7,
  "router_id": "11005a33-c5ac-4c96-ab6f-8f2827cc7da6",
  "status": "ACTIVE",
  "tags": [
    {
      "key": "my-tag",
      "read_only": false,
      "value": "my-tag-value"
    }
  ],
  "task_id": "a4eb4b29-048e-42f6-a5e1-2c18bc001c45",
  "updated_at": "2019-06-13T13:58:12+0000"
}