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/engine/engine.go

@@ -0,0 +1,67 @@
+//
+//  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 engine
+
+import (
+	"context"
+
+	"ragflow/internal/engine/types"
+)
+
+// EngineType document engine type
+type EngineType string
+
+const (
+	EngineElasticsearch EngineType = "elasticsearch"
+	EngineInfinity      EngineType = "infinity"
+)
+
+// SearchRequest is an alias for types.SearchRequest
+type SearchRequest = types.SearchRequest
+
+// SearchResponse is an alias for types.SearchResponse
+type SearchResponse = types.SearchResponse
+
+// DocEngine document storage engine interface
+type DocEngine interface {
+	// Search
+	Search(ctx context.Context, req interface{}) (interface{}, error)
+
+	// Index operations
+	CreateIndex(ctx context.Context, indexName string, mapping interface{}) error
+	DeleteIndex(ctx context.Context, indexName string) error
+	IndexExists(ctx context.Context, indexName string) (bool, error)
+
+	// Document operations
+	IndexDocument(ctx context.Context, indexName, docID string, doc interface{}) error
+	BulkIndex(ctx context.Context, indexName string, docs []interface{}) (interface{}, error)
+	GetDocument(ctx context.Context, indexName, docID string) (interface{}, error)
+	DeleteDocument(ctx context.Context, indexName, docID string) error
+
+	// Health check
+	Ping(ctx context.Context) error
+	Close() error
+}
+
+// Type returns the engine type (helper method for runtime type checking)
+// This is a workaround since we can't import elasticsearch or infinity packages directly
+func Type(docEngine DocEngine) EngineType {
+	// Type checking through interface methods is not straightforward
+	// This is a placeholder that should be implemented differently
+	// or rely on configuration to know the type
+	return EngineType("unknown")
+}