Hi,

it seems there is a slow memory leak with https urls. Consider the following script:

#!/usr/bin/env node
const axios = require('axios');
function pingUrl(url) {
  axios.get(url).then(res => { console.log(res.status); });
  setTimeout(pingUrl.bind(null, url), 1000);
}
pingUrl(process.argv[2]);

I ran two instances of the script in parallel, one with with an http url, the other with the same url in https.
After 20 hours, the https process uses 10% of my 16GB memory, compared to 0.1% for the http process.

We discovered this issue since we use axios as part of a home made monitoring tool. The tool pings urls at regular interval and we are having memory issues after a while.