Graceful Exit
func Notify(c chan<- os.Signal, sig ...os.Signal)
Notify causes package signal to relay incoming signals to c. If no signals are provided, all incoming signals will be relayed to c. Otherwise, just the provided signals will.
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.
It is allowed to call Notify multiple times with the same channel: each call expands the set of signals sent to that channel. The only way to remove signals from the set is to call Stop.
It is allowed to call Notify multiple times with different channels and the same signals: each channel receives copies of incoming signals independently.
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