process.go
func (p Process) Signal(sig os.Signal) error {
	if p.ops == nil {
		return newGenericError(fmt.Errorf("invalid process"), ProcessNotExecuted)
	}
	return p.ops.signal(sig)
}
func (p Process) Signal(sig os.Signal) error {
	if p.ops == nil {
		return newGenericError(fmt.Errorf("invalid process"), ProcessNotExecuted)
	}
	return p.ops.signal(sig)
}
// Signal sends a signal to the Process.