Use atomics to make writing of results safe in removeObjectsOneByOne

Previous implementation didn't have any synchronization mechanism for
goroutines that does the work.

There are multiple approaches to make it work correctly, let's start with
the simplest - atomics.

pkg/s3/client.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"fmt"
 	"net/url"
+	"sync/atomic"
 
 	"github.com/golang/glog"
 	"github.com/minio/minio-go/v7"
@@ -173,8 +174,8 @@ func (client *s3Client) removeObjectsOneByOne(bucketName, prefix string) error {
 	objectsCh := make(chan minio.ObjectInfo, 1)
 	guardCh := make(chan int, parallelism)
 	var listErr error
-	totalObjects := 0
-	removeErrors := 0
+	var totalObjects int64 = 0
+	var removeErrors int64 = 0
 
 	go func() {
 		defer close(objectsCh)
@@ -185,7 +186,7 @@ func (client *s3Client) removeObjectsOneByOne(bucketName, prefix string) error {
 				listErr = object.Err
 				return
 			}
-			totalObjects++
+			atomic.AddInt64(&totalObjects, 1)
 			objectsCh <- object
 		}
 	}()
@@ -202,7 +203,7 @@ func (client *s3Client) removeObjectsOneByOne(bucketName, prefix string) error {
 				minio.RemoveObjectOptions{VersionID: obj.VersionID})
 			if err != nil {
 				glog.Errorf("Failed to remove object %s, error: %s", obj.Key, err)
-				removeErrors++
+				atomic.AddInt64(&removeErrors, 1)
 			}
 			<- guardCh
 		}(object)