goprocess.go
func WithSignals(sig ...os.Signal) Process {
	p := WithParent(Background())
	c := make(chan os.Signal)
	signal.Notify(c, sig...)
	go func() {
		<-c
		signal.Stop(c)
		p.Close()
	}()
	return p
}
func WithSignals(sig ...os.Signal) Process {
	p := WithParent(Background())
	c := make(chan os.Signal)
	signal.Notify(c, sig...)
	go func() {
		<-c
		signal.Stop(c)
		p.Close()
	}()
	return p
}
// WithSignals returns a Process that will Close() when any given signal fires.
// This is useful to bind Process trees to syscall.SIGTERM, SIGKILL, etc.