- Reading the code of this delay writer implemenation, it looks like
that it should only actually write content to the `io.Writer` if x
amount of time has passed by. However in practice it was always printing
the buffer even if the X amount of time didn't pass yet. This is in line
with what was being said in the issue that this was to help with
https://github.com/go-gitea/gitea/issues/9610.
- This was caused by the extra `Close()` calls which in turn caused that
when the second `Close` is called (which is done in a defer already) it
would've printed the buffer anyway. So remove the extra calls to `Close()`.
- Add unit test.