race condition happens when using ONCE subscriptions about gnmic HOT 3 CLOSED

I saw that behavior once ( no pun intended ) but was never able to reproduce it.
It happens when the outputs are closed before the export method finishes.

The Write inside Export is async but Export itself is not async without a go routine call, the for loop would be waiting for Export to finish to get the next msg form the response channel.

2 options:

• Remove the go routine call to Export, but make the response channel buffered. Issue becomes how big of a buffer we need?
• Find a way to sync terminating c.Start() and running t.Export()

I will try to implement the second option.

from gnmic.

Ended up implementing the first one but just in case of ONCE subscription

from gnmic.

implemented in #71 and manually tested (2d4ff07).

from gnmic.