更新13.9 (#280)

* Update 07.3.md

* Update 07.3.md

* Update 07.6.md

* fix few problems

* Update 10.6 and 10.8

* Update 11.6 and 11.7

* fix some problems before Chap13

* add a dot

* Update 13.9

eBook/13.1.md

@@ -44,7 +44,7 @@ func main() {
 ```go
 func Sqrt(f float64) (float64, error) {
 	if f < 0 {
-		return 0, errors.New (“math - square root of negative number”)
+		return 0, errors.New ("math - square root of negative number")
 	}
    // implementation of Sqrt
 }
@@ -54,7 +54,7 @@ func Sqrt(f float64) (float64, error) {
 
 ```go
 if f, err := Sqrt(-1); err != nil {
-	fmt.Printf(“Error: %s\n”, err)
+	fmt.Printf("Error: %s\n", err)
 }
 ```
 
@@ -65,13 +65,13 @@ if f, err := Sqrt(-1); err != nil {
 ```go
 // PathError records an error and the operation and file path that caused it.
 type PathError struct {
-	Op string    // “open”, “unlink”, etc.
+	Op string    // "open", "unlink", etc.
 	Path string  // The associated file.
 	Err error  // Returned by the system call.
 }
 
 func (e *PathError) String() string {
-	return e.Op + “ ” + e.Path + “: “+ e.Err.Error()
+	return e.Op + " " + e.Path + ": "+ e.Err.Error()
 }
 ```
 
@@ -94,7 +94,7 @@ switch err := err.(type) {
 		PrintPathError(err)
 	...
 	default:
-		fmt.Printf(“Not a special error, just %s\n”, err)
+		fmt.Printf("Not a special error, just %s\n", err)
 }
 ```
 
@@ -115,7 +115,7 @@ func (e *SyntaxError) String() string { return e.msg }
 ```go
 if serr, ok := err.(*json.SyntaxError); ok {
 	line, col := findLine(f, serr.Offset)
-	return fmt.Errorf(“%s:%d:%d: %v”, f.Name(), line, col, err)
+	return fmt.Errorf("%s:%d:%d: %v", f.Name(), line, col, err)
 }
 ```
 
@@ -165,15 +165,15 @@ var (
 
 ```go
 if f < 0 {
-	return 0, fmt.Errorf(“math: square root of negative number %g”, f)
+	return 0, fmt.Errorf("math: square root of negative number %g", f)
 }
 ```
 
 第二个例子：从命令行读取输入时，如果加了 help 标志，我们可以用有用的信息产生一个错误：
 
 ```go
-if len(os.Args) > 1 && (os.Args[1] == “-h” || os.Args[1] == “--help”) {
-	err = fmt.Errorf(“usage: %s infile.txt outfile.txt”, filepath.Base(os.Args[0]))
+if len(os.Args) > 1 && (os.Args[1] == "-h" || os.Args[1] == "--help") {
+	err = fmt.Errorf("usage: %s infile.txt outfile.txt", filepath.Base(os.Args[0]))
 	return
 }
 ```