using RestSharp;


var options = new RestClientOptions("https://api.sandbox.{id}.gr4vy.app/checkout/sessions");
var client = new RestClient(options);
var request = new RestRequest("");
request.AddHeader("Authorization", "Bearer <token>");
request.AddJsonBody("{}", false);
var response = await client.PostAsync(request);

Console.WriteLine("{0}", response.Content);

package main

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

func main() {

	url := "https://api.sandbox.{id}.gr4vy.app/checkout/sessions"

	payload := strings.NewReader("{}")

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

	req.Header.Add("Authorization", "Bearer <token>")
	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.sandbox.{id}.gr4vy.app/checkout/sessions")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{}")
  .asString();

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.sandbox.{id}.gr4vy.app/checkout/sessions",
  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([
    
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json"
  ],
]);

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

curl_close($curl);

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

import requests

url = "https://api.sandbox.{id}.gr4vy.app/checkout/sessions"

payload = {}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({})
};

fetch('https://api.sandbox.{id}.gr4vy.app/checkout/sessions', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

curl --request POST \
  --url https://api.sandbox.{id}.gr4vy.app/checkout/sessions \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{}'

{
  "type": "checkout-session",
  "id": "8d3fe99b-1422-42e6-bbb3-932d95ae5f79",
  "expires_at": "2022-01-01T00:00:00+00:00",
  "cart_items": [
    {
      "name": "GoPro HERO9 Camcorder",
      "quantity": 1,
      "unit_amount": 37999,
      "discount_amount": 0,
      "tax_amount": 0,
      "external_identifier": "item-789123",
      "sku": "sku-789123",
      "product_url": "https://example.com/items/gopro",
      "image_url": "https://example.com/images/items/gopro.png",
      "categories": [
        "<string>"
      ],
      "product_type": "physical",
      "seller_country": "US"
    }
  ],
  "metadata": {
    "key": "value"
  },
  "airline": {
    "passenger_name_record": "JOHN L",
    "booking_code": "X36Q9C",
    "ticket_number": "123-1234-151555",
    "ticket_delivery_method": "other",
    "issued_at": "2013-07-16T19:23:00.000+00:00",
    "issued_address": "123 Broadway, New York",
    "travel_agency_code": "12345",
    "travel_agency_name": "Agency name",
    "travel_agency_invoice_number": "EG15555155",
    "travel_agency_plan_name": "B733",
    "restricted_ticket": false,
    "issuing_carrier_code": "A3",
    "issuing_carrier_name": "Aegean Airlines",
    "issuing_iata_designator": "A3",
    "issuing_icao_code": "AEE",
    "reservation_system": "Amadeus",
    "is_cardholder_traveling": false,
    "passengers": [
      {
        "title": "Mr.",
        "first_name": "John",
        "last_name": "Lunn",
        "email_address": "john@example.com",
        "phone_number": "+1234567890",
        "passport_number": "7700225",
        "ticket_number": "LH1236699999",
        "frequent_flyer_number": "15885566",
        "date_of_birth": "2013-07-16",
        "age_group": "adult"
      }
    ],
    "legs": [
      {
        "carrier_code": "LY",
        "carrier_name": "El Al Israel Airlines",
        "iata_designator": "LY",
        "icao_code": "ELY",
        "flight_number": "BA98",
        "departure_at": "2013-07-16T19:23:00.000+00:00",
        "departure_country": "UK",
        "departure_city": "London",
        "departure_airport": "LHR",
        "arrival_at": "2013-07-16T19:23:00.000+00:00",
        "arrival_country": "UK",
        "arrival_city": "London",
        "arrival_airport": "LHR",
        "fare_basis_code": "WH7LNR",
        "flight_class": "E",
        "stop_over": false,
        "route_type": "round_trip",
        "coupon_number": "15885566",
        "fare_amount": 100,
        "fee_amount": 100,
        "tax_amount": 100,
        "departure_tax_amount": 100,
        "seat_class": "F"
      }
    ]
  },
  "payment_method": {
    "type": "payment_method",
    "id": "<string>",
    "method": "card",
    "scheme": "visa",
    "label": "4242",
    "details": {
      "bin": "411111",
      "card_type": "credit",
      "card_country": "US",
      "card_issuer_name": "Bank"
    },
    "fingerprint": "20eb353620155d2b5fc864cc46a73ea77cb92c725238650839da1813fa987a17"
  }
}

{
  "type": "error",
  "code": "unauthorized",
  "status": 401,
  "message": "No valid API authentication found",
  "details": []
}

{
  "type": "error",
  "code": "duplicate_record",
  "status": 409,
  "message": "A duplicate record exists with this external_identifier value",
  "details": []
}