fix indent

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 @@ func funcName(params string) gin.HandlerFunc {
           c.Set("TestVar", params)
           c.Next()    
       }
-}
-```
+  }
+  ```
 
 ## Execution process