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

var encoding = Buffer.from(authKey + ':' + accountToken).toString('base64');
var req = unirest('POST', "https://<subdomain>/v2/accounts/"+accountSid+"/contacts")
  .headers({
	  Authorization: 'Basic ' + encoding,
	  'Content-Type': 'application/json'
  })
  .send(JSON.stringify({"contacts":[
      {
				"number":"+919100YYYY10",
				"first_name":"captain",
				"last_name":"exotel",
				"company_name":"Exotel",
				"email":"captain@email.com",
				"tag":"Member",
				"custom_field":{
						"key":{"key1":"values1"}
					}
			},
			{
				"number":"+919100XXXX10",
				"first_name":"captain",
				"last_name":"exotel",
				"company_name":"Exotel",
				"email":"captain@email.com",
				"tag":"Technician",
				"custom_field":{
					"key":{"key1":"values1"}
				}
			}
		]}))
  .end(function (res) { 
    if (res.error) throw new Error(res.error); 
    console.log(res.raw_body);
  });

<?php

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

$encoding = base64_encode($authKey .":". $accountToken);

curl_setopt_array($curl, array(
  CURLOPT_URL => 'https://<subdomain>/v2/accounts/exotel8u3/contacts',
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => '',
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 0,
  CURLOPT_FOLLOWLOCATION => true,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => 'POST',
  CURLOPT_POSTFIELDS =>'{
    "contacts": [
        {
            "number": "+919100YYYY10",
            "first_name": "captain",
            "last_name": "exotel",
            "company_name": "Exotel",
            "email": "captain@email.com",
            "tag": "Member",
            "custom_field": {
                "key": {
                    "key1": "values1"
                }
            }
        },
        {
            "number": "+919100XXXX10",
            "first_name": "captain",
            "last_name": "exotel",
            "company_name": "Exotel",
            "email": "captain@email.com",
            "tag": "Technician",
            "custom_field": {
                "key": {
                    "key1": "values1"
                }
            }
        }
    ]
}',
  CURLOPT_HTTPHEADER => array(
    "Authorization: Basic ".$encoding,
    'Content-Type: application/json'
  ),
));

$response = curl_exec($curl);

curl_close($curl);
echo $response;

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

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

url = "https://<subdomain>/v2/accounts/"+ accountSid+"/contacts"

payload = json.dumps({
    "contacts": [
        {
            "number": "+919100YYYY10",
            "first_name": "captain",
            "last_name": "exotel",
            "company_name": "Exotel",
            "email": "captain@email.com",
            "tag": "Member",
            "custom_field": {
                "key": {
                    "key1": "values1"
                }
            }
        },
        {
            "number": "+919100XXXX10",
            "first_name": "captain",
            "last_name": "exotel",
            "company_name": "Exotel",
            "email": "captain@email.com",
            "tag": "Technician",
            "custom_field": {
                "key": {
                    "key1": "values1"
                }
            }
        }
    ]
})

headers = {
    'Authorization': "Basic " + encoding,
    'Content-Type': 'application/json'
}


response = requests.request("POST", 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"
	"strings"
)

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://<subdomain>/v2/accounts/" + accountSid + "/contacts"
	method := "POST"

	payload := strings.NewReader(`{
    "contacts": [
        {
            "number": "+919100000010",
            "first_name": "captain",
            "last_name": "exotel",
            "company_name": "Exotel",
            "email": "captain@email.com",
            "tag": "Member",
            "custom_field": {
                "key": {
                    "key1": "values1"
                }
            }
        },
        {
            "number": "+919100000010",
            "first_name": "captain",
            "last_name": "exotel",
            "company_name": "Exotel",
            "email": "captain@email.com",
            "tag": "Member",
            "custom_field": {
                "key": {
                    "key1": "values1"
                }
            }
        }
    ]
}`)

	client := &http.Client{}
	req, err := http.NewRequest(method, url, payload)

	if err != nil {
		fmt.Println(err)
		return
	}
	req.Header.Add("Content-Type", "application/json")
	req.Header.Add("Authorization", "Basic "+encoding)

	res, err := client.Do(req)
	if err != nil {
		fmt.Println(err)
		return
	}
	defer res.Body.Close()

	body, err := ioutil.ReadAll(res.Body)
	if err != nil {
		fmt.Println(err)
		return
	}
	fmt.Println(string(body))
}