proposal: net/http/httputil/v2: split into focused subpackages

[bcmills]

This proposal builds on #7907 (remove deprecated stuff) and #19660 (refactor ioutil to provide a coherent abstraction).

httputil currently contains:

• Dump{Request,RequestOut,Response}: "It should only be used by servers to debug client requests." These would be clearer in a net/http/debug subpackage.
• NewChunked{Reader,Writer}: "not needed by normal applications. The http package automatically decodes chunking when reading response bodies." Not obvious why it's exported, but it could easily go in a net/http/chunked subpackage.
• ReverseProxy: Could easily go in a separate net/http/proxy subpackage.
• BufferPool: has ~nothing to do with HTTP, and if it is still useful implies a garbage-collector issue that we should address instead.
• ClientConn: "We should have deleted it before Go 1."
• ServerConn: "We should have deleted it before Go 1."

(@bradfitz)

[bradfitz]

Is it open season on filing bugs about everything that's wrong in the standard library?

[bcmills]

Yep. :)

Just want to make sure we don't miss anything. (It's like grocery shopping: if I don't make a list I'll forget all the important stuff.)

[ianlancetaylor]

Should this be handled as part of #5465?

[bcmills]

I think the concrete suggestions here are mostly orthogonal to net/http proper.

It is clearly related, though: if the corresponding interfaces change, then that certainly impacts the utilities that hook into and/or implement those interfaces.