curl --request POST \
  --url https://api.gcore.com/cloud/v1/volumes/{project_id}/{region_id}/{volume_id}/detach \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: application/json' \
  --data '{
  "instance_id": "169942e0-9b53-42df-95ef-1a8b6525c2bd"
}'

{
  "attachments": [
    {
      "attached_at": "2019-07-26T14:22:03+0000",
      "attachment_id": "f2ed59d9-8068-400c-be4b-c4501ef6f33c",
      "device": "/dev/vda",
      "flavor_id": "g1-standard-1-2",
      "instance_name": "instance-1",
      "server_id": "8dc30d49-bb34-4920-9bbd-03a2587ec0ad",
      "volume_id": "67baa7d1-08ea-4fc5-bef2-6b2465b7d227"
    }
  ],
  "bootable": false,
  "created_at": "2019-05-29T05:32:41+0000",
  "creator_task_id": "d74c2bb9-cea7-4b23-a009-2f13518ae66d",
  "id": "726ecfcc-7fd0-4e30-a86e-7892524aa483",
  "is_root_volume": false,
  "limiter_stats": {
    "MBps_base_limit": 50,
    "MBps_burst_limit": 200,
    "iops_base_limit": 1000,
    "iops_burst_limit": 5000
  },
  "name": "volume-1",
  "project_id": 1,
  "region": "Luxembourg",
  "region_id": 1,
  "size": 50,
  "snapshot_ids": [
    "<string>"
  ],
  "status": "available",
  "tags": [
    {
      "key": "my-tag",
      "read_only": false,
      "value": "my-tag-value"
    }
  ],
  "task_id": "<string>",
  "updated_at": "2019-05-29T05:39:20+0000",
  "volume_image_metadata": {
    "checksum": "ba3cd24377dde5dfdd58728894004abb",
    "container_format": "bare",
    "disk_format": "raw",
    "image_id": "723037e2-ec6d-47eb-92de-6276c8907839",
    "image_name": "cirros-gcloud",
    "min_disk": "1",
    "min_ram": "0",
    "size": "46137344"
  },
  "volume_type": "standard"
}