var request = require("request");
var accountSid = "XXXXXXXXX";
var accountToken = "YYYYYYYYY";
var authKey = "ZZZZZZZZZZ";

var encoding = Buffer.from(authKey + ':' + accountToken).toString('base64')
var options = { method: 'GET',
  url: 'https://api.exotel.com/v2/accounts/'+ accountSid +'/campaigns/491dd6c97d64475ba0ce346a18530ce5',
  headers: 
   { 
     Authorization: 'Basic ' + encoding 
    } };

request(options, function (error, response, body) {
  if (error) throw new Error(error);

  console.log(body);
  
});

<?php
$curl = curl_init();
$accountSid = "XXXXXXXXXX";
$accountToken = "YYYYYYYYYY";
$authKey = "ZZZZZZZZZZ";

$encoding = base64_encode($authKey .":". $accountToken);
curl_setopt_array($curl, array(
  CURLOPT_URL => "https://api.exotel.com/v2/accounts/".$accountSid."/campaigns/491dd6c97d64475ba0ce346a18530ce5",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "GET",
  CURLOPT_POSTFIELDS => "",
  CURLOPT_HTTPHEADER => array(
    "Authorization: Basic ".$encoding
  ),
));

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

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

import requests, base64, json
accountSid = "XXXXXXXXX"
authToken = "YYYYYYYYY"
authKey = "ZZZZZZZZZZ"

encoding = base64.b64encode(authKey + ":" + authToken)

url = "https://api.exotel.com/v2/accounts/"+ accountSid +"/campaigns/491dd6c97d64475ba0ce346a18530ce5"

payload = ""
headers = {
    'Authorization': "Basic " + encoding
    }

response = requests.request("GET", url, data=payload, headers=headers)
print(response.text)
print(json.dumps(json.loads(response.text), indent = 4, sort_keys = True))

package main

import (
	b64 "encoding/base64"
	"fmt"
	"io/ioutil"
	"net/http"
)

func main() {

	// Please provide accountSid, authToken from your Exotel account
	accountSid := "XXXXXXXXX"
	authToken := "YYYYYYYY"
	authKey := "ZZZZZZZZZZ"

	// Encoding the accountSid and authToken, used in Authorization header
	encoding := b64.StdEncoding.EncodeToString([]byte(authKey + ":" + authToken))

	url := "https://api.exotel.com/v2/accounts/" + accountSid + "/campaigns/491dd6c97d64475ba0ce346a18530ce5"

	req, _ := http.NewRequest("GET", url, nil)

	req.Header.Add("Authorization", "Basic "+encoding)

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

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

	fmt.Println(res)
	fmt.Println(string(body))
}