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

import requests

url = "https://api.gcore.com/cloud/v1/volumes/{project_id}/{region_id}/{volume_id}/attach"

payload = {
    "instance_id": "169942e0-9b53-42df-95ef-1a8b6525c2bd",
    "attachment_tag": "boot"
}
headers = {
    "Authorization": "<api-key>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: '<api-key>', 'Content-Type': 'application/json'},
  body: JSON.stringify({instance_id: '169942e0-9b53-42df-95ef-1a8b6525c2bd', attachment_tag: 'boot'})
};

fetch('https://api.gcore.com/cloud/v1/volumes/{project_id}/{region_id}/{volume_id}/attach', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.gcore.com/cloud/v1/volumes/{project_id}/{region_id}/{volume_id}/attach",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'instance_id' => '169942e0-9b53-42df-95ef-1a8b6525c2bd',
    'attachment_tag' => 'boot'
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: <api-key>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.gcore.com/cloud/v1/volumes/{project_id}/{region_id}/{volume_id}/attach"

	payload := strings.NewReader("{\n  \"instance_id\": \"169942e0-9b53-42df-95ef-1a8b6525c2bd\",\n  \"attachment_tag\": \"boot\"\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "<api-key>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://api.gcore.com/cloud/v1/volumes/{project_id}/{region_id}/{volume_id}/attach")
  .header("Authorization", "<api-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"instance_id\": \"169942e0-9b53-42df-95ef-1a8b6525c2bd\",\n  \"attachment_tag\": \"boot\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.gcore.com/cloud/v1/volumes/{project_id}/{region_id}/{volume_id}/attach")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = '<api-key>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"instance_id\": \"169942e0-9b53-42df-95ef-1a8b6525c2bd\",\n  \"attachment_tag\": \"boot\"\n}"

response = http.request(request)
puts response.read_body

{
  "bootable": false,
  "created_at": "2019-05-29T05:32:41+0000",
  "id": "726ecfcc-7fd0-4e30-a86e-7892524aa483",
  "is_root_volume": false,
  "name": "volume-1",
  "project_id": 1,
  "region": "Luxembourg",
  "region_id": 1,
  "size": 50,
  "tags": [
    {
      "key": "my-tag",
      "read_only": false,
      "value": "my-tag-value"
    }
  ],
  "volume_type": "standard",
  "attachments": [
    {
      "attachment_id": "f2ed59d9-8068-400c-be4b-c4501ef6f33c",
      "volume_id": "67baa7d1-08ea-4fc5-bef2-6b2465b7d227",
      "attached_at": "2019-07-26T14:22:03+0000",
      "device": "/dev/vda",
      "flavor_id": "g1-standard-1-2",
      "instance_name": "instance-1",
      "server_id": "8dc30d49-bb34-4920-9bbd-03a2587ec0ad"
    }
  ],
  "creator_task_id": "d74c2bb9-cea7-4b23-a009-2f13518ae66d",
  "limiter_stats": {
    "MBps_base_limit": 50,
    "MBps_burst_limit": 200,
    "iops_base_limit": 1000,
    "iops_burst_limit": 5000
  },
  "snapshot_ids": [
    "<string>"
  ],
  "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"
  }
}