修复nginx lua 导入模块的问题

nginx.conf

@@ -92,14 +92,14 @@ http {
                 local ext = string.match(filename, "%.([^%.]+)$")
                 local mime_type
                 
-                local detect = require "detect_mime_by_magic"
+                local detect_module = require "detect_mime_by_magic"
                 if ext then
                     -- mime_type = get_mime_type(ext)
                     -- 有扩展名,用download下载
                     return ngx.exec("/download/" .. filename)
                 else
                     -- 无扩展名：用 Lua 魔数检测
-                    mime_type = detect(filepath)
+                    mime_type = detect_module.detect(filepath)
                 end
 
                 -- 3. 设置响应头