Translate chapter 64
Translate chapter 64

Chapter 64 translation. I'm not sure whether `버퍼링된 채널` is good
choice for translation of `Buffered channel`.
Let's discuss about it later.

Signed-off-by: SeongJae Park <4e244449b52bf6ddddd07d261eea0e61e60df45e@gmail.com>

atomaths/go-tour-translator,atomaths/go-tour-translator