Merge pull request #83 from Hongbo-Miao/patch-2

chore: update switch case code format

ch5/ch5-09.md

@@ -8,12 +8,12 @@ Go的类型系统会在编译时捕获很多错误，但有些错误只能在运
 
 ```Go
 switch s := suit(drawCard()); s {
-	case "Spades":                                // ...
-	case "Hearts":                                // ...
-	case "Diamonds":                              // ...
-	case "Clubs":                                 // ...
-	default:
-		panic(fmt.Sprintf("invalid suit %q", s)) // Joker?
+case "Spades":                                // ...
+case "Hearts":                                // ...
+case "Diamonds":                              // ...
+case "Clubs":                                 // ...
+default:
+	panic(fmt.Sprintf("invalid suit %q", s)) // Joker?
 }
 ```