Doesn't get env variable in the gatsby-plugin-support-chat package inside node_modules

Question

I installed gatsby-plugin-support-chat and followed the tutorial from here (https://www.gatsbyjs.com/plugins/gatsby-plugin-support-chat).

When I run npx ngrok http 8000, and try to send message in the chat-bot, then it occurs 500 error like this.

Module parse failed: Unexpected token (4:13)
You may need an appropriate loader to handle this file type, currently no      
loaders are configured to process this file. See
https://webpack.js.org/concepts#loaders
| import { WebClient } from "@slack/web-api"
|
> let channelID: string = process.env.CHANNEL_ID
| let token: string = process.env.SLACK_TOKEN

Absolutely, I added 2 above env variables in the env.development file and checked them using the console in the component file.

This error just occurs in the \node_modules\gatsby-plugin-support-chat\src\api\gatsby-plugin-support-chat\send-message.ts.

The content of send-message.ts is like this

import { GatsbyFunctionRequest, GatsbyFunctionResponse } from "gatsby"
import { WebClient } from "@slack/web-api"

let channelID: string = process.env.CHANNEL_ID
let token: string = process.env.SLACK_TOKEN

const web = new WebClient(token)

interface SlackRequest {
  channel: string
  text: string
  thread_ts?: string
}

export default async function handler(
  req: GatsbyFunctionRequest,
  res: GatsbyFunctionResponse
) {
  if (req.method != "POST") {
    return res.status(401).json({
      message: "Use post method",
    })
  }
  let requestData: SlackRequest

  try {
    if (req.body.thread_ts != null) {
      requestData = {
        channel: channelID,
        text: req.body.message,
        thread_ts: req.body.thread_ts,
      }
    } else {
      requestData = { channel: channelID, text: req.body.message }
    }
    const result = await web.chat.postMessage(requestData).then(res => {
      return res
    })
    res.json(result)
  } catch (error) {
    console.log(error)
    res.status(500).send(error)
  }
}

Does anyone know this issue solution? Thanks