curl --request POST \
  --url https://api.gcore.com/cloud/v1/floatingips/{project_id}/{region_id}/{floating_ip_id}/assign \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "port_id": "ee2402d0-f0cd-4503-9b75-69be1d11c5f1",
  "fixed_ip_address": "192.168.10.15"
}
'

import requests

url = "https://api.gcore.com/cloud/v1/floatingips/{project_id}/{region_id}/{floating_ip_id}/assign"

payload = {
    "port_id": "ee2402d0-f0cd-4503-9b75-69be1d11c5f1",
    "fixed_ip_address": "192.168.10.15"
}
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({
    port_id: 'ee2402d0-f0cd-4503-9b75-69be1d11c5f1',
    fixed_ip_address: '192.168.10.15'
  })
};

fetch('https://api.gcore.com/cloud/v1/floatingips/{project_id}/{region_id}/{floating_ip_id}/assign', 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/floatingips/{project_id}/{region_id}/{floating_ip_id}/assign",
  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([
    'port_id' => 'ee2402d0-f0cd-4503-9b75-69be1d11c5f1',
    'fixed_ip_address' => '192.168.10.15'
  ]),
  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/floatingips/{project_id}/{region_id}/{floating_ip_id}/assign"

	payload := strings.NewReader("{\n  \"port_id\": \"ee2402d0-f0cd-4503-9b75-69be1d11c5f1\",\n  \"fixed_ip_address\": \"192.168.10.15\"\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/floatingips/{project_id}/{region_id}/{floating_ip_id}/assign")
  .header("Authorization", "<api-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"port_id\": \"ee2402d0-f0cd-4503-9b75-69be1d11c5f1\",\n  \"fixed_ip_address\": \"192.168.10.15\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.gcore.com/cloud/v1/floatingips/{project_id}/{region_id}/{floating_ip_id}/assign")

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  \"port_id\": \"ee2402d0-f0cd-4503-9b75-69be1d11c5f1\",\n  \"fixed_ip_address\": \"192.168.10.15\"\n}"

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

{
  "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"
}