Make Golang correctly delete temp files during uploading (#36128) (#36129)

Fix #36127

Partially backport #36128
And by the way partially backport  #36017

routers/common/middleware.go

@@ -71,8 +71,11 @@ func RequestContextHandler() func(h http.Handler) http.Handler {
 			req = req.WithContext(cache.WithCacheContext(ctx))
 			ds.SetContextValue(httplib.RequestContextKey, req)
 			ds.AddCleanUp(func() {
-				if req.MultipartForm != nil {
-					_ = req.MultipartForm.RemoveAll() // remove the temp files buffered to tmp directory
+				// The req in context might have changed due to the new req.WithContext calls
+				// For example: in NewBaseContext, a new "req" with context is created, and the multipart-form is parsed there.
+				ctxReq := ds.GetContextValue(httplib.RequestContextKey).(*http.Request)
+				if ctxReq.MultipartForm != nil {
+					_ = ctxReq.MultipartForm.RemoveAll() // remove the temp files buffered to tmp directory
 				}
 			})
 			next.ServeHTTP(respWriter, req)