gexec/session.go
func (s *Session) Signal(signal os.Signal) *Session {
	if s.processIsAlive() {
		s.Command.Process.Signal(signal)
	}
	return s
}
func (s *Session) Signal(signal os.Signal) *Session {
	if s.processIsAlive() {
		s.Command.Process.Signal(signal)
	}
	return s
}
/*
Signal sends the running command the passed in signal.  It does not wait for the process to exit.

If the command has already exited, Signal returns silently.

The session is returned to enable chaining.
*/