fix: coding style and file format for chapter 11, 12, 13, 14 and 15.

eBook/exercises/chapter_11/main_stack_v2.go

@@ -1,17 +1,17 @@
-// main_stack_v2.go
-package main
-
-import (
-    "./stack/collection"
-    "fmt"
-)
-
-func main() {
-    var s collection.Stack
-    s.Push("world")
-    s.Push("hello, ")
-    for s.Size() > 0 {
-        fmt.Print(s.Pop())
-    }
-    fmt.Println()
-}
+// main_stack_v2.go
+package main
+
+import (
+	"./stack/collection"
+	"fmt"
+)
+
+func main() {
+	var s collection.Stack
+	s.Push("world")
+	s.Push("hello, ")
+	for s.Size() > 0 {
+		fmt.Print(s.Pop())
+	}
+	fmt.Println()
+}