const axios = require("axios"),
    axiosInstance = axios.create(),

    // view the webhook result @ https://webhook.site/#!/a9845fd3-dfca-4dda-aa4c-0cd5e7a092b2
    // or get new webhook endpoint and replace the following.
    webhookUrl = 'https://webhook.site/a9845fd3-dfca-4dda-aa4c-0cd5e7a092b2';

// Global Config
axios.defaults.headers.common['User-Agent'] = 'global-bug-test/1.0.0';

// Instance Config
axiosInstance.defaults.headers.common['User-Agent'] = 'instance-bug-test/1.0.0';

// GET request to webhook url
let req = await axios.get(webhookUrl);
console.log(`global user agent: ${req.request.getHeader('User-Agent')}`); // expected to be "global-bug-test/1.0.0"

req = await axiosInstance.get(webhookUrl);
console.log(`instance user agent: ${req.request.getHeader('User-Agent')}`); // expected to be "instance-bug-test/1.0.0"

req = await axios({
    method: 'get',
    url: webhookUrl,
    headers: {
        'User-Agent': 'per-req/1.0.0'
    }
});
console.log(`per request user agent: ${req.request.getHeader('User-Agent')}`); // as expected 'per-req/1.0.0'

req = await axiosInstance({
    method: 'get',
    url: webhookUrl,
    headers: {
        'User-Agent': 'instance-per-req/1.0.0'
    }
});
console.log(`instance per request user agent: ${req.request.getHeader('User-Agent')}`); // as expected 'instance-per-req/1.0.0'