update docs

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

@@ -8,26 +8,26 @@ 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
+```go
-  func funcName(params string) gin.HandlerFunc {
+func funcName(params string) gin.HandlerFunc {
-      // <---
+    // <---
-      // This is part one
+    // This is part one
-      // --->
+    // --->
-      // The follow code is an example
+    // The follow code is an example
-      if err := check(params); err != nil {
+    if err := check(params); err != nil {
-          panic(err)
+        panic(err)
-      }
+    }
 
-      return func(c *gin.Context) {
+    return func(c *gin.Context) {
-          // <---
+        // <---
-          // This is part two
+        // This is part two
-          // --->
+        // --->
-          // The follow code is an example
+        // The follow code is an example
-          c.Set("TestVar", params)
+        c.Set("TestVar", params)
-          c.Next()    
+        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
+```