curl --request POST \
  --url https://sandbox.cashfree.com/api/v2/subscriptions/{subReferenceId}/activate \
  --header 'Content-Type: application/json' \
  --header 'X-Client-Id: <x-client-id>' \
  --header 'X-Client-Secret: <x-client-secret>' \
  --data '
{
  "nextScheduledOn": "2021-12-17"
}
'

import requests

url = "https://sandbox.cashfree.com/api/v2/subscriptions/{subReferenceId}/activate"

payload = { "nextScheduledOn": "2021-12-17" }
headers = {
    "X-Client-Id": "<x-client-id>",
    "X-Client-Secret": "<x-client-secret>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {
    'X-Client-Id': '<x-client-id>',
    'X-Client-Secret': '<x-client-secret>',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({nextScheduledOn: '2021-12-17'})
};

fetch('https://sandbox.cashfree.com/api/v2/subscriptions/{subReferenceId}/activate', 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://sandbox.cashfree.com/api/v2/subscriptions/{subReferenceId}/activate",
  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([
    'nextScheduledOn' => '2021-12-17'
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json",
    "X-Client-Id: <x-client-id>",
    "X-Client-Secret: <x-client-secret>"
  ],
]);

$response = curl_exec($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://sandbox.cashfree.com/api/v2/subscriptions/{subReferenceId}/activate"

	payload := strings.NewReader("{\n  \"nextScheduledOn\": \"2021-12-17\"\n}")

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

	req.Header.Add("X-Client-Id", "<x-client-id>")
	req.Header.Add("X-Client-Secret", "<x-client-secret>")
	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://sandbox.cashfree.com/api/v2/subscriptions/{subReferenceId}/activate")
  .header("X-Client-Id", "<x-client-id>")
  .header("X-Client-Secret", "<x-client-secret>")
  .header("Content-Type", "application/json")
  .body("{\n  \"nextScheduledOn\": \"2021-12-17\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://sandbox.cashfree.com/api/v2/subscriptions/{subReferenceId}/activate")

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

request = Net::HTTP::Post.new(url)
request["X-Client-Id"] = '<x-client-id>'
request["X-Client-Secret"] = '<x-client-secret>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"nextScheduledOn\": \"2021-12-17\"\n}"

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