curl --request POST \
  --url https://api.centralcart.io/v1/webstore/upsells \
  --header 'Content-Type: application/json' \
  --header 'x-store-domain: <x-store-domain>' \
  --data '
{
  "cart": [
    1,
    3
  ],
  "placement": "CHECKOUT"
}
'

import requests

url = "https://api.centralcart.io/v1/webstore/upsells"

payload = {
    "cart": [1, 3],
    "placement": "CHECKOUT"
}
headers = {
    "x-store-domain": "<x-store-domain>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {'x-store-domain': '<x-store-domain>', 'Content-Type': 'application/json'},
  body: JSON.stringify({cart: [1, 3], placement: 'CHECKOUT'})
};

fetch('https://api.centralcart.io/v1/webstore/upsells', 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.centralcart.io/v1/webstore/upsells",
  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([
    'cart' => [
        1,
        3
    ],
    'placement' => 'CHECKOUT'
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json",
    "x-store-domain: <x-store-domain>"
  ],
]);

$response = curl_exec($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.centralcart.io/v1/webstore/upsells"

	payload := strings.NewReader("{\n  \"cart\": [\n    1,\n    3\n  ],\n  \"placement\": \"CHECKOUT\"\n}")

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

	req.Header.Add("x-store-domain", "<x-store-domain>")
	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.centralcart.io/v1/webstore/upsells")
  .header("x-store-domain", "<x-store-domain>")
  .header("Content-Type", "application/json")
  .body("{\n  \"cart\": [\n    1,\n    3\n  ],\n  \"placement\": \"CHECKOUT\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.centralcart.io/v1/webstore/upsells")

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

request = Net::HTTP::Post.new(url)
request["x-store-domain"] = '<x-store-domain>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"cart\": [\n    1,\n    3\n  ],\n  \"placement\": \"CHECKOUT\"\n}"

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

[
  {
    "id": 7,
    "name": "Chave Bônus",
    "slug": "chave-bonus",
    "pricing": {
      "price": 5,
      "compare_at": 15
    },
    "upsell": {
      "type": "ADDITIONAL",
      "source": "product",
      "upsell_trigger_id": 1,
      "offer_price": 5,
      "original_price": 15,
      "has_discount": true,
      "in_cart": false
    }
  }
]

{
  "errors": [
    {
      "message": "Store not found."
    }
  ]
}