update docs

docs/how-to-build-an-effective-middleware.md

@@ -8,8 +8,8 @@ The middleware has two parts:
 
   - part two is what executes on every request. For example, a database middleware you simply inject your "global" database object into the context. Once it's inside the context, you can retrieve it from within other middlewares and your handler furnction.
 
-  ```go
-  func funcName(params string) gin.HandlerFunc {
+```go
+func funcName(params string) gin.HandlerFunc {
     // <---
     // This is part one
     // --->
@@ -26,8 +26,8 @@ The middleware has two parts:
         c.Set("TestVar", params)
         c.Next()    
     }
-  }
-  ```
+}
+```
 
 ## Execution process
 
@@ -41,8 +41,6 @@ func main() {
 
 	router.GET("/rest/n/api/*some", mid1(), mid2(), handler)
 
-	fmt.Println("end")
-
 	router.Run()
 }
 
@@ -81,3 +79,59 @@ func mid2() gin.HandlerFunc {
 	}
 }
 ```
+
+According to [Consitituent part](#consitituent-part) said, when we run the gin process, **part one** will execute firstly and will print the follow information:
+
+```go
+globalMiddleware...1
+mid1...1
+mid2...1
+```
+
+And init order are:
+
+```go
+globalMiddleware...1
+    |
+    v
+mid1...1
+    |
+    v
+mid2...1
+```
+
+When we curl one request `curl -v localhost:8080/rest/n/api/some`, **part two** will execute their middleware and output the following information:
+
+```go
+globalMiddleware...2
+mid1...2
+mid2...2
+exec handler.
+mid2...3
+mid1...3
+globalMiddleware...3
+```
+
+In other words, run order are:
+
+```go
+globalMiddleware...2
+    |
+    v
+mid1...2
+    |
+    v
+mid2...2
+    |
+    v
+exec handler.
+    |
+    v
+mid2...3
+    |
+    v
+mid1...3
+    |
+    v
+globalMiddleware...3
+```