fix: use buffered os.Signal channel as argument to signal.Notify

[haoqixu]

Use buffered os.Signal channel as argument to signal.Notify to ensure that we do not drop a signal notification.

[haoel]

Thanks for this PR, cloud you please let me understand the situation which could drop the signal notification?

[haoqixu]

https://pkg.go.dev/os/signal#Notify:

Package signal will not block sending to c: the caller must ensure that c has sufficient buffer space to keep up with the expected signal rate. For a channel used for notification of just one signal value, a buffer of size 1 is sufficient.

Any signal which arrives after signal.Notify but before <-done will get discarded. It is just technically possible and not a big problem here.

[haoel]

Thanks for this explanation