Generate a hex encoded HMAC-SHA256 hash using Crypto in Nodejs

import { Service } from './service';
import crypto from 'crypto';

export class TestService extends Service {
    private _secretKey: string;

    constructor() {
        this._secretKey = '1234567890';
		this._userId = '123';
    }

    /**
     * Get Hex encoded hash of secret key
     */
    private GetHashKey(): string {
        return crypto
            .createHmac('sha256', this._secretKey)
            .update(this._getUserString(this._userId))
            .digest('hex');
    }
}