修复了远程请求错误，优化了日志警告信息，并改进了生成默认etag的逻辑。

README.md

@@ -1,7 +1,6 @@
 # 自定义webp-server-go
 
-1. 如果源站没有`etag`, 添加一个默认值, 这是防止很多源站不方便配置;
-2. 如果文件非图片类型, 302重定向到源文件
+1. 如果文件非图片类型, 302重定向到源文件
 
 <p align="center">
 	<img src="./pics/webp_server.png"/>

handler/remote.go

@@ -121,37 +121,23 @@ func fetchRemoteImg(url string, subdir string) config.MetaFile {
 }
 
 func pingURL(url string) string {
+	// this function will try to return identifiable info, currently include etag, content-length as string
+	// anything goes wrong, will return ""
 	var etag, length string
 	resp, err := http.Head(url)
 	if err != nil {
-			log.Errorf("Connection to remote error when pingUrl: %v", err)
-			return generateFallbackIdentifier(url)
+		log.Errorln("Connection to remote error when pingUrl!")
+		return ""
 	}
 	defer resp.Body.Close()
 
 	if resp.StatusCode == fiber.StatusOK {
-			etag = resp.Header.Get("ETag")
-			length = resp.Header.Get("Content-Length")
-			
-			if etag == "" {
-					log.Warn("Remote didn't return ETag in header, using Last-Modified if available")
-					etag = resp.Header.Get("Last-Modified")
-			}
-			
-			if etag == "" {
-					log.Warn("Neither ETag nor Last-Modified available, using fallback identifier")
-					etag = generateFallbackIdentifier(url)
-			}
-	} else {
-			log.Warnf("Unexpected status code: %d when pinging URL: %s", resp.StatusCode, url)
-			return generateFallbackIdentifier(url)
+		etag = resp.Header.Get("etag")
+		length = resp.Header.Get("content-length")
+	}
+	if etag == "" {
+		log.Info("Remote didn't return etag in header when getRemoteImageInfo, please check.")
 	}
-
 	return etag + length
 }
 
-func generateFallbackIdentifier(url string) string {
-	// 使用 URL 的哈希值作为稳定的标识符
-	return "fallback-" + helper.HashString(url)
-}
-