windows/debug/svc: buffer channel passed to signal.Notify

The os/signal package drops signal notifications if the channel is not
ready to receive immediately. To avoid dropping signals (for example,
while processing the other branch of a 'select'), the channel must be
buffered.

This fixes a mistake flagged by 'go vet ./...'.

Change-Id: I2a20dbe2aa27ae8ec009fff5e7be47e4409fdddd
Reviewed-on: https://go-review.googlesource.com/c/sys/+/465595
Auto-Submit: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Quim Muntal <quimmuntal@gmail.com>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

Author: Bryan C. Mills

windows/svc/debug/service.go

@@ -23,7 +23,7 @@ func Run(name string, handler svc.Handler) error {
 	cmds := make(chan svc.ChangeRequest)
 	changes := make(chan svc.Status)
 
-	sig := make(chan os.Signal)
+	sig := make(chan os.Signal, 1)
 	signal.Notify(sig)
 
 	go func() {