Add dnsLookupIpVersion option

[Giotino]

Checklist

• I have read the documentation.
• I have included a pull request description of my changes.

I've added the documentation relative to the family property. I've also added a stricter type definition.

I think the name "family" it's a little generic, it might be renamed to "IPfamily" or something like that.

Fixes #1263

[Giotino]

I've added some IPv6 (and DNS) related tests.

It seems like Travis CI is missing IPv6 support, event on loopback.

[Giotino]

Since family (now ipVersion) is only related to DNS I think it should be renamed to something like dnsIpVersion or resolvedIpVersion.

[sindresorhus]

Can you also add a util.deprecate call if family option is used?

[Giotino]

Can you also add a util.deprecate call if family option is used?

According to the Node.JS documentation util.deprecrate is made for functions.
https://nodejs.org/api/util.html#util_util_deprecate_fn_msg_code

[sindresorhus]

There are benefits to util.deprecate. It only prints the warning once and it's also possible to silence it. Maybe we could make an utility that works the same way?

[...] that will emit a DeprecationWarning using the 'warning' event. The warning will be emitted and printed to stderr the first time the returned function is called. After the warning is emitted, the wrapped function is called without emitting a warning.

[Giotino]

I'm working on the "deprecation utilty" in this PR #1255
When it's ok I'll merge it here.

[sindresorhus]

This looks good except for the missing deprecation warning.

[szmarczak]

https://travis-ci.com/github/sindresorhus/got/jobs/341303159#L480

  Unhandled rejection in test/http.ts

  › ClientRequest.<anonymous> (dist/source/core/index.js:72:256)

  › ClientRequest.origin.emit (node_modules/@szmarczak/http-timer/dist/source/index.js:39:20)

  › emitErrorNT (internal/streams/destroy.js:100:8)

  › emitErrorCloseNT (internal/streams/destroy.js:68:3)

[szmarczak]

the stack trace is mangled so you have to run the tests without nyc

[Giotino]

There was a race condition on the two await new Promise (in http and https) used for the tests related to DeprecationWarning.
The promise could have been resolved before the request was resolved, resulting in the destruction of the web server while the request was still running.

[sindresorhus]

Very nice work, @Giotino 👌

[szmarczak]

@sindresorhus Maybe let's use numbers but undefined means 'auto'? That way there would be no 0.

[sindresorhus]

Yeah, that would be nicer.