RAGFlow go API server (#13240)

# RAGFlow Go Implementation Plan 🚀

This repository tracks the progress of porting RAGFlow to Go. We'll
implement core features and provide performance comparisons between
Python and Go versions.

## Implementation Checklist

- [x] User Management APIs
- [x] Dataset Management Operations
- [x] Retrieval Test
- [x] Chat Management Operations
- [x] Infinity Go SDK

---------

Signed-off-by: Jin Hai <haijin.chn@gmail.com>
Co-authored-by: Yingfeng Zhang <yingfeng.zhang@gmail.com>

internal/handler/error.go

@@ -0,0 +1,46 @@
+//
+//  Copyright 2026 The InfiniFlow Authors. All Rights Reserved.
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+//
+
+package handler
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	"go.uber.org/zap"
+
+	"ragflow/internal/logger"
+)
+
+// HandleNoRoute handles requests to undefined routes
+func HandleNoRoute(c *gin.Context) {
+	// Log the request details on server side
+	logger.Logger.Warn("The requested URL was not found",
+		zap.String("method", c.Request.Method),
+		zap.String("path", c.Request.URL.Path),
+		zap.String("query", c.Request.URL.RawQuery),
+		zap.String("remote_addr", c.ClientIP()),
+		zap.String("user_agent", c.Request.UserAgent()),
+	)
+
+	// Return JSON error response
+	c.JSON(http.StatusNotFound, gin.H{
+		"code":    404,
+		"message": "Not Found: " + c.Request.URL.Path,
+		"data":    nil,
+		"error":   "Not Found",
+	})
+}