ch7: fix code format

ch7/ch7-14.md

@@ -4,17 +4,17 @@
 
 這里顯示的是和這個API相關的部分：
 
+<u><i>encoding/xml</i></u>
 ```go
-encoding/xml
 package xml
 
 type Name struct {
-    Local string // e.g., "Title" or "id"
+	Local string // e.g., "Title" or "id"
 }
 
 type Attr struct { // e.g., name="value"
-    Name  Name
-    Value string
+	Name  Name
+	Value string
 }
 
 // A Token includes StartElement, EndElement, CharData,
@@ -37,55 +37,55 @@ func (*Decoder) Token() (Token, error) // returns next Token in sequence
 
 下面的xmlselect程序獲取和打印在一個XML文檔樹中確定的元素下找到的文本。使用上面的API，它可以在輸入上一次完成它的工作而從來不要具體化這個文檔樹。
 
+<u><i>gopl.io/ch7/xmlselect</i></u>
 ```go
-gopl.io/ch7/xmlselect
 // Xmlselect prints the text of selected elements of an XML document.
 package main
 
 import (
-    "encoding/xml"
-    "fmt"
-    "io"
-    "os"
-    "strings"
+	"encoding/xml"
+	"fmt"
+	"io"
+	"os"
+	"strings"
 )
 
 func main() {
-    dec := xml.NewDecoder(os.Stdin)
-    var stack []string // stack of element names
-    for {
-        tok, err := dec.Token()
-        if err == io.EOF {
-            break
-        } else if err != nil {
-            fmt.Fprintf(os.Stderr, "xmlselect: %v\n", err)
-            os.Exit(1)
-        }
-        switch tok := tok.(type) {
-        case xml.StartElement:
-            stack = append(stack, tok.Name.Local) // push
-        case xml.EndElement:
-            stack = stack[:len(stack)-1] // pop
-        case xml.CharData:
-            if containsAll(stack, os.Args[1:]) {
-                fmt.Printf("%s: %s\n", strings.Join(stack, " "), tok)
-            }
-        }
-    }
+	dec := xml.NewDecoder(os.Stdin)
+	var stack []string // stack of element names
+	for {
+		tok, err := dec.Token()
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			fmt.Fprintf(os.Stderr, "xmlselect: %v\n", err)
+			os.Exit(1)
+		}
+		switch tok := tok.(type) {
+		case xml.StartElement:
+			stack = append(stack, tok.Name.Local) // push
+		case xml.EndElement:
+			stack = stack[:len(stack)-1] // pop
+		case xml.CharData:
+			if containsAll(stack, os.Args[1:]) {
+				fmt.Printf("%s: %s\n", strings.Join(stack, " "), tok)
+			}
+		}
+	}
 }
 
 // containsAll reports whether x contains the elements of y, in order.
 func containsAll(x, y []string) bool {
-    for len(y) <= len(x) {
-        if len(y) == 0 {
-            return true
-        }
-        if x[0] == y[0] {
-            y = y[1:]
-        }
-        x = x[1:]
-    }
-    return false
+	for len(y) <= len(x) {
+		if len(y) == 0 {
+			return true
+		}
+		if x[0] == y[0] {
+			y = y[1:]
+		}
+		x = x[1:]
+	}
+	return false
 }
 ```
 
@@ -122,8 +122,8 @@ type Node interface{} // CharData or *Element
 type CharData string
 
 type Element struct {
-    Type     xml.Name
-    Attr     []xml.Attr
-    Children []Node
+	Type     xml.Name
+	Attr     []xml.Attr
+	Children []Node
 }
 ```