Create authentication ticket for Sinch Android And IOS client (Nodejs)

I am facing problem in creating the Sinch auth ticket for Android and IOS client using Nodejs. I tried sinch-ticketgen NPM module but it is generating tickets for javascript only, we can not use this ticket for Android and IOS clients.

Following is the code snippet I am using for the ticket generation but it is not working,

const crypto = require('crypto');
const shasum = crypto.createHash('sha1');

const key = '0b25bb2d-f5dd-4337-9f99-a318196f886a';
const secret = 'm1aur2Q4FUWWNuMlKq3KKg==';
const userId = 'sanket';
const sequence = 0;

const stringToSign = userId + key + sequence + secret;

shasum.update(stringToSign);

const singnature = shasum.digest('utf8'); //utf8
console.log('Signature ', singnature.toString('base64'));
const token = singnature.toString('base64').trim();

console.log(token);

Pseducode for the ticket generation is given in the https://www.sinch.com/docs/voice/ios/#applicationauthentication

I tried java example its working fine, not getting where I am making mistake in Nodejs ticket creation.

Following is the working Nodejs snippet for it.

    const crypto = require('crypto');
    const shasum = crypto.createHash('sha1');

    const key = '0b25bb2d-f5dd-4337-9f99-a318196f886a';
    const secret = 'm1aur2Q4FUWWNuMlKq3KKg==';
    const userId = 'sanket';
    const sequence = 0;

    const stringToSign = userId + key + sequence + secret;

    shasum.update(stringToSign);

    const singnature = shasum.digest();
    console.log('Signature ', singnature.toString('base64'));
    const token = singnature.toString('base64').trim();

    console.log(token);