clarify doc example

exhaustive.go

@@ -31,22 +31,24 @@ using explicit values, or by any means of declaring a valid Go const. It is
 allowed for multiple enum members for a given enum type to have the same
 constant value.
 
-    type Command int
-    const (
-        Build Command = iota
-        Test
-    )
-    const Default = Build
-
 Definition of exhaustiveness
 
 A switch statement that switches on a value of an enum type is exhaustive if all
 of the enum type's members are listed in the switch statement's cases. If
 multiple enum member constants have the same constant value, it is sufficient
 for any one of these same-valued members to be listed.
 
+	type Command int
+    const (
+        Build Command = iota
+        Test
+        Default = Build
+    )
+
     func f(cmd Command) {
         // This switch statement is exhaustive.
+        // (The enum member Default does not have to be listed, because
+        // it has the same value as Build.)
         switch cmd {
         case Build:
         case Test: