process.go
func (p Process) Pid() (int, error) {
	// math.MinInt32 is returned here, because it's invalid value
	// for the kill() system call.
	if p.ops == nil {
		return math.MinInt32, newGenericError(fmt.Errorf("invalid process"), ProcessNotExecuted)
	}
	return p.ops.pid(), nil
}
func (p Process) Pid() (int, error) {
	// math.MinInt32 is returned here, because it's invalid value
	// for the kill() system call.
	if p.ops == nil {
		return math.MinInt32, newGenericError(fmt.Errorf("invalid process"), ProcessNotExecuted)
	}
	return p.ops.pid(), nil
}
// Pid returns the process ID