How can i fix CORS error firebase function

Question

I currently have a CORS problem that I can't solve, here is my code:

gogologo.js

const souscription = async (req, res) => {
  if (!req.body.data || !req.body.data.souscrireParams) {
    console.error('souscription  input error')
    res.json({ data: { error: 'souscription input error' } })
    return

  }
  const souscrireParams = req.body.data.souscrireParams
  console.log('souscription:', JSON.stringify(req.body.data.souscrireParams))

  var data = JSON.stringify(souscrireParams)
  const headers = {
    'x-api-key': apiKey,
    'Content-Type': 'application/json'
  }
  var reqConfig = {
    method: 'post',
    url: 'url',
    headers: headers,
    data: data
  };
  console.log("reqConfig = ", reqConfig)
  try {
    const response = await axios(reqConfig)
    const result = response.data
    if (result.resultat === 'success') {
      res.json({ data: result })
    } else {
      const msg = {
        to: 'mail',
        from: 'mail',
        subject: 'souscription Fail',
        html: `deal <br><br> ${JSON.stringify(souscrireParams)}<br><br>Error:<br><br>`,
      }
      sgMail.setApiKey(sgKey)
      await sgMail.send(msg)
      res.json({ data: { error: { message: 'souscrire error' } } })

    }

  } catch (error) {
    console.log('error message : ', error.message)
    console.log('error  : ', error)
    const msg = {
      to: 'mail',
      from: 'mail',
      subject: 'souscription fail',
      html: `deal <br><br> ${JSON.stringify(souscrireParams)}<br><br>Error:<br><br>${JSON.stringify({ error: error.message })}`,
    }
    sgMail.setApiKey(sgKey)
    await sgMail.send(msg)
    res.json({ data: { error: error.message } })
  }

}

exports.souscription = souscription

index.js

exports.souscription = functions.runWith({
   vpcConnector: 'app-functions-connector',
   vpcConnectorEgressSettings: 'ALL_TRAFFIC'
}).https.onRequest(async (req, res) => {
  console.log('souscription IP:', await publicIp.v4())
  cors(req, res, async () => {
    gogologo.souscription(req, res)
  })
})

when I press the subscribe button, it displays an error message "Access to fetch at 'url genereted by firebase function' from origin 'url app' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled." with a post error.