ch8: fix code format

ch8/ch8-05.md

@@ -2,9 +2,10 @@
 
 本節中，我們會探索一些用來在併行時循環迭代的常見併發模型。我們會探究從全尺寸圖片生成一些縮略圖的問題。gopl.io/ch8/thumbnail包提供了ImageFile函數來幫我們拉伸圖片。我們不會説明這個函數的實現，隻需要從gopl.io下載它。
 
+<u><i>gopl.io/ch8/thumbnail</i></u>
 ```go
-gopl.io/ch8/thumbnail
 package thumbnail
+
 // ImageFile reads an image from infile and writes
 // a thumbnail-size version of it in the same directory.
 // It returns the generated file name, e.g., "foo.thumb.jpg".
@@ -13,15 +14,15 @@ func ImageFile(infile string) (string, error)
 
 下面的程序會循環迭代一些圖片文件名，併爲每一張圖片生成一個縮略圖：
 
+<u><i>gopl.io/ch8/thumbnail</i></u>
 ```go
-gopl.io/ch8/thumbnail
 // makeThumbnails makes thumbnails of the specified files.
 func makeThumbnails(filenames []string) {
-    for _, f := range filenames {
-        if _, err := thumbnail.ImageFile(f); err != nil {
-            log.Println(err)
-        }
-    }
+	for _, f := range filenames {
+		if _, err := thumbnail.ImageFile(f); err != nil {
+			log.Println(err)
+		}
+	}
 }
 ```
 
@@ -32,9 +33,9 @@ func makeThumbnails(filenames []string) {
 ```go
 // NOTE: incorrect!
 func makeThumbnails2(filenames []string) {
-    for _, f := range filenames {
-        go thumbnail.ImageFile(f) // NOTE: ignoring errors
-    }
+	for _, f := range filenames {
+		go thumbnail.ImageFile(f) // NOTE: ignoring errors
+	}
 }
 ```
 
@@ -45,29 +46,28 @@ func makeThumbnails2(filenames []string) {
 ```go
 // makeThumbnails3 makes thumbnails of the specified files in parallel.
 func makeThumbnails3(filenames []string) {
-    ch := make(chan struct{})
-    for _, f := range filenames {
-        go func(f string) {
-            thumbnail.ImageFile(f) // NOTE: ignoring errors
-            ch <- struct{}{}
-        }(f)
-    }
-    // Wait for goroutines to complete.
-    for range filenames {
-        <-ch
-    }
+	ch := make(chan struct{})
+	for _, f := range filenames {
+		go func(f string) {
+			thumbnail.ImageFile(f) // NOTE: ignoring errors
+			ch <- struct{}{}
+		}(f)
+	}
+	// Wait for goroutines to complete.
+	for range filenames {
+		<-ch
+	}
 }
 ```
 
 註意我們將f的值作爲一個顯式的變量傳給了函數，而不是在循環的閉包中聲明：
 
-
 ```go
 for _, f := range filenames {
-    go func() {
-        thumbnail.ImageFile(f) // NOTE: incorrect!
-        // ...
-    }()
+	go func() {
+		thumbnail.ImageFile(f) // NOTE: incorrect!
+		// ...
+	}()
 }
 ```
 
@@ -79,22 +79,22 @@ for _, f := range filenames {
 // makeThumbnails4 makes thumbnails for the specified files in parallel.
 // It returns an error if any step failed.
 func makeThumbnails4(filenames []string) error {
-    errors := make(chan error)
+	errors := make(chan error)
 
-    for _, f := range filenames {
-        go func(f string) {
-            _, err := thumbnail.ImageFile(f)
-            errors <- err
-        }(f)}
-    }
+	for _, f := range filenames {
+		go func(f string) {
+			_, err := thumbnail.ImageFile(f)
+			errors <- err
+		}(f)}
+	}
 
-    for range filenames {
-        if err := <-errors; err != nil {
-            return err // NOTE: incorrect: goroutine leak!
-        }
-    }
+	for range filenames {
+		if err := <-errors; err != nil {
+			return err // NOTE: incorrect: goroutine leak!
+		}
+	}
 
-    return nil
+	return nil
 }
 ```
 
@@ -108,31 +108,30 @@ func makeThumbnails4(filenames []string) error {
 // makeThumbnails5 makes thumbnails for the specified files in parallel.
 // It returns the generated file names in an arbitrary order,
 // or an error if any step failed.
-
 func makeThumbnails5(filenames []string) (thumbfiles []string, err error) {
-    type item struct {
-        thumbfile string
-        err       error
-    }
+	type item struct {
+		thumbfile string
+		err       error
+	}
 
-    ch := make(chan item, len(filenames))
-    for _, f := range filenames {
-        go func(f string) {
-            var it item
-            it.thumbfile, it.err = thumbnail.ImageFile(f)
-            ch <- it
-        }(f)
-    }
+	ch := make(chan item, len(filenames))
+	for _, f := range filenames {
+		go func(f string) {
+			var it item
+			it.thumbfile, it.err = thumbnail.ImageFile(f)
+			ch <- it
+		}(f)
+	}
 
-    for range filenames {
-        it := <-ch
-        if it.err != nil {
-            return nil, it.err
-        }
-        thumbfiles = append(thumbfiles, it.thumbfile)
-    }
+	for range filenames {
+		it := <-ch
+		if it.err != nil {
+			return nil, it.err
+		}
+		thumbfiles = append(thumbfiles, it.thumbfile)
+	}
 
-    return thumbfiles, nil
+	return thumbfiles, nil
 }
 ```
 
@@ -144,35 +143,34 @@ func makeThumbnails5(filenames []string) (thumbfiles []string, err error) {
 // makeThumbnails6 makes thumbnails for each file received from the channel.
 // It returns the number of bytes occupied by the files it creates.
 func makeThumbnails6(filenames <-chan string) int64 {
-    sizes := make(chan int64)
-    var wg sync.WaitGroup // number of working goroutines
-    for f := range filenames {
-        wg.Add(1)
-        // worker
-        go func(f string) {
-            defer wg.Done()
-            thumb, err := thumbnail.ImageFile(f)
-            if err != nil {
-                log.Println(err)
-                return
-            }
-            info, _ := os.Stat(thumb) // OK to ignore error
-            sizes <- info.Size()
-        }(f)
-    }
+	sizes := make(chan int64)
+	var wg sync.WaitGroup // number of working goroutines
+	for f := range filenames {
+		wg.Add(1)
+		// worker
+		go func(f string) {
+			defer wg.Done()
+			thumb, err := thumbnail.ImageFile(f)
+			if err != nil {
+				log.Println(err)
+				return
+			}
+			info, _ := os.Stat(thumb) // OK to ignore error
+			sizes <- info.Size()
+		}(f)
+	}
 
-    // closer
-    go func() {
-        wg.Wait()
-        close(sizes)
-    }()
+	// closer
+	go func() {
+		wg.Wait()
+		close(sizes)
+	}()
 
-
-    var total int64
-    for size := range sizes {
-        total += size
-    }
-    return total
+	var total int64
+	for size := range sizes {
+		total += size
+	}
+	return total
 }
 ```