How to add more API endpoints

[addreeh]

Hi, I would like to know how can I add more endpoints, for example when visiting api/hello, I would like to automate something, for example call to greeting command.
I tried this:

import express, { Request, Response } from 'express'
import { startVercel } from '../src'
import { whey, casein } from '../src/scraper/scraper'
import { sendMessage, sendError } from '../src/scraper/telegram'
import { Product } from '../src/interfaces'
import { manage, insert, update } from '../src/scraper/postgres'
import { VercelRequest, VercelResponse } from '@vercel/node'

const app = express()

// enable JSON body parser
app.use(express.json())

// Handle requests to the root URL to check if the server is running
app.get('/', (req: Request, res: Response) => {
  res.send('<h1>Server is running!</h1>')
})

// Handle requests to the root URL for Vercel function and other routes
app.all('*', async (req: Request | VercelRequest, res: Response | VercelResponse, next: Function) => {
  try {
    if ((req as VercelRequest).query !== undefined) {
      // If it's a Vercel request, handle it using the startVercel function
      await startVercel(req as VercelRequest, res as VercelResponse)
    } else {
      // If it's not a Vercel request, continue to the next middleware
      next()
    }
  } catch (e: any) {
    res.status(500).send('<h1>Server Error</h1><p>Sorry, there was a problem</p>')
    console.error(e.message)
  }
})

// Handle requests to /evowhey endpoint
app.get('/evowhey', async (req: Request, res: Response) => {
  try {
    const product: Product = await whey()

    const message = `*HSN |* [${product.product}](${product.link}) *| ${product.price.replace('.', ',')}€*`

    await manage(product).then(async result => {
      if (result.rows.length === 0) {
        await insert(product).then(() => {
          void sendMessage(message)
        }).catch((error: string) => {
          console.log(error)
          void sendError(error)
        })
      } else {
        product.price = '26.10'
        await update(product).then((result) => {
          console.log(result)
          const updatedMessage = `*HSN |* [${product.product}](${product.link}) *|* ${result.originalPrice} *➜ ${product.price.replace('.', ',')}€*${result.message}`
          void sendMessage(updatedMessage)
        }).catch((error: string) => {
          console.log(error)
          void sendError(error)
        })
      }
    })

    res.send(product)
  } catch (error) {
    console.error('Error fetching Evowhey:', error)
    res.status(500).send('Error fetching Evowhey')
  }
})

// Handle requests to /casein endpoint
app.get('/casein', async (req: Request, res: Response) => {
  try {
    const result = await casein()
    res.send(result)
  } catch (error) {
    console.error('Error fetching Casein:', error)
    res.status(500).send('Error fetching Casein')
  }
})

export default app

But its not working, I dont know if maybe I have to add something to vercel.json or any other file.
Thanks.