func (p *fixedPool) ID() string {
	return p.id
}
ID implements Stage.
package pipeline
import (
	"context"
	"fmt"
	"sync"
)
type fixedPool struct {
	id    string
	fifos []Stage
}
func FixedPool(id string, task Task, num int) Stage {
	if num <= 0 {
		return nil
	}
	fifos := make([]Stage, num)
	for i := 0; i < num; i++ {
		fifos[i] = FIFO("", task)
	}
	return &fixedPool{
		id:    id,
		fifos: fifos,
	}
}