Fix: Data Race Bug detected via TestConcurrenyDownloadIndex

Signed-off-by: haojingcn <mhjlq1989@gmail.com>

pkg/repo/v1/chartrepo.go

@@ -28,6 +28,7 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 
 	"helm.sh/helm/v4/internal/fileutil"
 	"helm.sh/helm/v4/pkg/getter"
@@ -53,6 +54,7 @@ type ChartRepository struct {
 	IndexFile *IndexFile
 	Client    getter.Getter
 	CachePath string
+	mutex     sync.RWMutex
 }
 
 // NewChartRepository constructs ChartRepository
@@ -77,6 +79,9 @@ func NewChartRepository(cfg *Entry, getters getter.Providers) (*ChartRepository,
 
 // DownloadIndexFile fetches the index from a repository.
 func (r *ChartRepository) DownloadIndexFile() (string, error) {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+
 	indexURL, err := ResolveReferenceURL(r.Config.URL, "index.yaml")
 	if err != nil {
 		return "", err