close targetSocket when proxy replies with non-200 status

[arenevier]

Fixes issue #560

[jancurn]

This looks reasonable, thanks for the fix

[jancurn]

@jirimoravcik what do you think?

[jirimoravcik]

Hey @arenevier, can you please provide minimal reproduction code that wouldn't close before this fix and would close with the fix? Thank you

[arenevier]

Hey @arenevier, can you please provide minimal reproduction code that wouldn't close before this fix and would close with the fix? Thank you

Here is an example. If I send SIGINT, the server will close. But node process will hang and won't exit properly.

import * as ProxyChain from 'proxy-chain';     ■ Cannot find module 'proxy-chain' or its corresponding type declarations.
  
  async function main() {
  
    const server = new ProxyChain.Server({
      port: 6000,
      host: '127.0.0.1',
H     prepareRequestFunction: (params) => {     ■■ 'params' is declared but its value is never read.
            return {
              upstreamProxyUrl: "http://some.proxy.that.returns.403"
            };
      },
    });
  
    ['SIGINT', 'SIGTERM'].forEach((signal) => {
E     process.once(signal, async () => {     ■ Cannot find name 'process'. Do you need to install type definitions for node? Try `npm i --save-dev
        console.log('got signal', signal);
        // close the server gracefully
        await server.close(true);
      });
    });
  }
  
  main();