add swagger demo

cmd/open_im_api/docs/swagger.json

@@ -0,0 +1,62 @@
+{
+    "swagger": "2.0",
+    "info": {
+        "description": "This is a sample server celler server.",
+        "title": "Swagger Example API",
+        "termsOfService": "http://swagger.io/terms/",
+        "contact": {
+            "name": "API Support",
+            "url": "http://www.swagger.io/support",
+            "email": "support@swagger.io"
+        },
+        "license": {
+            "name": "Apache 2.0",
+            "url": "http://www.apache.org/licenses/LICENSE-2.0.html"
+        },
+        "version": "1.0"
+    },
+    "host": "localhost:8080",
+    "basePath": "/api/v1",
+    "paths": {
+        "/hello": {
+            "get": {
+                "description": "向你说Hello",
+                "consumes": [
+                    "application/json"
+                ],
+                "tags": [
+                    "测试"
+                ],
+                "summary": "测试SayHello",
+                "parameters": [
+                    {
+                        "type": "string",
+                        "description": "人名",
+                        "name": "who",
+                        "in": "query",
+                        "required": true
+                    }
+                ],
+                "responses": {
+                    "200": {
+                        "description": "{\"msg\": \"hello Razeen\"}",
+                        "schema": {
+                            "type": "string"
+                        }
+                    },
+                    "400": {
+                        "description": "{\"msg\": \"who are you\"}",
+                        "schema": {
+                            "type": "string"
+                        }
+                    }
+                }
+            }
+        }
+    },
+    "securityDefinitions": {
+        "BasicAuth": {
+            "type": "basic"
+        }
+    }
+}