Connecting through a proxy

[delvedor]

This pr adds a test and the documentation to show how to connect through a proxy :)
I had to remove the super complex regex as it was not validating all absolute urls (eg: http://localhost:8080 didn't pass the check). I think that lazily checking the protocol is enough, as trying to save all users from themselves is impossible.

/cc @szmarczak
Closes #427

[mcollina]

Would you mind to show how to use it with Pool?

It would really be nice to also include some ways of having a ProxyAgent.

[delvedor]

It works in the exact same way with both Client and Pool, so I've added an additional test and a note in the docs :)

[mcollina]

Here is an example for the Agent API:

import { request, setGlobalAgent, ProxyAgent } from 'undici'

setGlobalAgent(new ProxyAgent('https://my.proxy.agent/'))

const {
  statusCode,
  headers,
  trailers,
  body
  // send the request via the proxy
} = await request('http://localhost:3000/foo')

console.log('response received', statusCode)
console.log('headers', headers)

for await (const data of body) {
  console.log('data', data)
}

console.log('trailers', trailers)

[codecov-io]

Codecov Report

Merging #568 (f9603f3) into master (1cae429) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #568      +/-   ##
==========================================
- Coverage   99.57%   99.57%   -0.01%     
==========================================
  Files          16       16              
  Lines        1400     1399       -1     
==========================================
- Hits         1394     1393       -1     
  Misses          6        6              

Impacted Files	Coverage Δ
lib/core/request.js	100.00% <100.00%> (ø)

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[mcollina]

FYI, you don't need to add the ProxyAgent right now. It can be another issue.

[mcollina]

lgtm

[budarin]

is there an example with proxying a POST request?

[mcollina]

No but it would be a good PR.