Fix unterminated chunk code

[hannahhoward]

Goals

While our go integration tests showed our unterminated chunk code to indicate a premature close was working, curl and wire-shark showed a different story.

The old code was simply taking the conn and writing a "0\r\n" to it. However, it wasn't closing the conn, and because we hadn't told golang's HTTP code that we were taking over the conn, after our handler completed, go would still write the termination code: "0\r\n\r\n". So what we'd end up with is a response that ended "0\r\n0\r\n\r\n".

after "0\r\n" is written, everything before \r\n is a trailer header. Go's HTTP client attempts to parse trailer headers, so when it read the second "0\r\n" it would error cause it's an incorrectly formatted header (the source of our weird "malformed MIME header" error message we've been seeing in tests).

however, node, curl, and browser clients ignore this portion and just make sure the response terminates, so they would see the /r/n and consider it valid.

Implementation

We need to actually close the connection, which also means "Hijack"ing it so go's http server doesn't try to keep using it.

This PR does that and fixes the problem of early terminating chunked streams correctly.

[willscott]

thanks for tracking down / catching!

[codecov-commenter]

Codecov Report

Merging #301 (11ed6b7) into main (fe9e760) will increase coverage by 0.31%.
The diff coverage is 45.45%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #301      +/-   ##
==========================================
+ Coverage   72.55%   72.87%   +0.31%     
==========================================
  Files          68       68              
  Lines        6217     6252      +35     
==========================================
+ Hits         4511     4556      +45     
+ Misses       1458     1450       -8     
+ Partials      248      246       -2     

Impacted Files	Coverage Δ
pkg/server/http/ipfs.go	63.08% <45.45%> (-0.85%)	⬇️

... and 7 files with indirect coverage changes

[hannahhoward]

two commits I pushed have no shown up on this PR due to: https://www.githubstatus.com/ -- some problem with PRs