func NewLogListRefresher(llPath string) LogListRefresher {
	return NewCustomLogListRefresher(&http.Client{Timeout: httpClientTimeout}, llPath)
}
NewLogListRefresher creates and inits a LogListRefresherImpl instance using
default http.Client
package submission
import (
	"bytes"
	"fmt"
	"net/http"
	"sync"
	"time"
	"github.com/google/certificate-transparency-go/loglist2"
	"github.com/google/certificate-transparency-go/x509util"
)
const (
	httpClientTimeout = 10 * time.Second
)
type LogListData struct {
	JSON         []byte
	List         *loglist2.LogList
	DownloadTime time.Time
}
type LogListRefresher interface {
	Refresh() (*LogListData, error)
	LastJSON() []byte
	Source() string
}
type logListRefresherImpl struct {
	updateMu sync.RWMutex
	lastJSON []byte
	path     string
	client   *http.Client
}
func NewCustomLogListRefresher(client *http.Client, llPath string) LogListRefresher {
	return &logListRefresherImpl{
		path:   llPath,
		client: client,
	}
}