Switch to `async: true` instead of `async: :once` since it causes memory issues

[binarylogic]

This fixes a memory issue with a dependency library (:hackney) where setting the async: :once option causes memory to continually grow. Using async: true does not have this same effect.

[jszwedko]

Aha, interesting, I see async: :once would tell it to only read receive once:

Note 1: When {async, once} is used the socket will receive only once. To receive the other messages use the function hackney:stream_next/1.

I assume there was still data left on the socket?

Does this have any implications for keep-alive / http pipelining?

[binarylogic]

Yeah, I spoke with @mitchellhenke about this yesterday, apparently this is meant to be manually read / closed. You need to use :hackney.stream_next/1 and :hackney.async_stop/1 when you're done. I still prefer this new method since what's outline here has more opportunity for failure and missed cleanup.

[jszwedko]

Gotcha :+1: