func (b ZeroBackoff) Next(retry int) (time.Duration, bool) {
	return 0, true
}
Next implements BackoffFunc for ZeroBackoff.
package elastic
import (
	"math"
	"math/rand"
	"sync"
	"time"
)
type BackoffFunc func(retry int) (time.Duration, bool)
type Backoff interface {
	Next(retry int) (time.Duration, bool)
}
type ZeroBackoff struct{}