Heroku Nodejs "Cannot GET"

Question

I made a CRUD with Nodejs, Express, Handlebars and Mongodb - Works great in development, but when I try to make the Deploy in Heroku from the continuous error "Cannot GET /".

I’ve researched a lot of materials that actually report problems, but I haven’t been able to fix them yet.

Can you help me ?

Follow my config:

app.js

// Models
const express = require('express')
const handlebars = require('express-handlebars')
const app = express()
const admin = require('./routes/admin')
const path = require('path')
const mongoose = require('mongoose')
const session = require('express-session')
const flash = require('connect-flash')
const dotenv = require('dotenv')
dotenv.config()
const mongoURI = process.env.mongoURI

// Express
app.use(express.urlencoded({
  extended: true
}))
app.use(express.json())

// Mongoose
mongoose.Promise = global.Promise
mongoose.connect(mongoURI, {
  useNewUrlParser: true,
  useCreateIndex: true,
  useUnifiedTopology: true,
  useFindAndModify: false
}).then(() => {
  console.log("Conectado com sucessoao MongoDB!")
}).catch((err) => {
  console.log("Erro ao se conectar ao MongoDB: " + err)
})

// Public
app.use(express.static(path.join(__dirname, 'public')))

// Routes
app.use('/admin', admin)

// Others
const PORT = process.env.PORT || 8081
app.listen(PORT, () => {
  console.log("Servidor rodando!")
})



package.json:

{
  "name": "cadastro_cli",
  "version": "1.0.0",
  "main": "app.js",
  "dependencies": {
    "connect-flash": "^0.1.1", "dotenv": "^10.0.0", "express": "^4.17.1", "express-handlebars": "^5.3.2", "express-session": "^1.17.2", "handlebars": "^4.7.7", "mongoose": "^5.13.3", "nodemon": "^2.0.12", "path": "^0.12.7"
  }
  ,
  "devDependencies": {
    "nodemon": "^2.0.12"
  }
  ,
  "scripts": {
    "start": "node app.js"
  }
  ,
  "engines": {
    "node": "13.14.0", "npm": "6.14.4"
  }
  ,
  "author": "@alexcamposwd",
  "license": "MIT",
  "description": ""
}