doc: provide example filepath.Walk for go1

R=golang-dev, r, r
CC=golang-dev
https://golang.org/cl/5674067

doc/go1.html

@@ -1540,12 +1540,24 @@ instead of a <code>Visitor</code> interface value.
 The <code>WalkFunc</code> function will be called even for files or directories that could not be opened;
 in such cases the error argument will describe the failure.
 If a directory's contents are to be skipped,
-the function should return the value <code>SkipDir</code>.
+the function should return the value <a href="/pkg/path/filepath/#variables"><code>filepath.SkipDir</code></a>
 </p>
 
-<p>
-<font color="red">TODO: add an example?</font>
-</p>
+<pre><!--{{code "progs/go1.go" `/STARTWALK/` `/ENDWALK/`}}
+-->    markFn := func(path string, info os.FileInfo, err error) error {
+        if path == &#34;pictures&#34; { // Will skip walking of directory pictures and its contents.
+            return filepath.SkipDir
+        }
+        if err != nil {
+            return err
+        }
+        log.Println(path)
+        return nil
+    }
+    err := filepath.Walk(&#34;.&#34;, markFn)
+    if err != nil {
+        log.Fatal(err)
+    }</pre>
 
 <p>
 <em>Updating</em>:

doc/go1.tmpl

@@ -1439,12 +1439,10 @@ instead of a <code>Visitor</code> interface value.
 The <code>WalkFunc</code> function will be called even for files or directories that could not be opened;
 in such cases the error argument will describe the failure.
 If a directory's contents are to be skipped,
-the function should return the value <code>SkipDir</code>.
+the function should return the value <a href="/pkg/path/filepath/#variables"><code>filepath.SkipDir</code></a>
 </p>
 
-<p>
-<font color="red">TODO: add an example?</font>
-</p>
+{{code "progs/go1.go" `/STARTWALK/` `/ENDWALK/`}}
 
 <p>
 <em>Updating</em>:

doc/progs/go1.go

@@ -12,6 +12,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"path/filepath"
 	"testing"
 	"time"
 	"unicode"
@@ -28,6 +29,7 @@ func main() {
 	runeType()
 	errorExample()
 	timePackage()
+	walkExample()
 	osIsExist()
 }
 
@@ -183,6 +185,25 @@ func timePackage() {
 	sleepUntil(time.Now().Add(123 * time.Millisecond))
 }
 
+func walkExample() {
+	// STARTWALK OMIT
+	markFn := func(path string, info os.FileInfo, err error) error {
+		if path == "pictures" { // Will skip walking of directory pictures and its contents.
+			return filepath.SkipDir
+		}
+		if err != nil {
+			return err
+		}
+		log.Println(path)
+		return nil
+	}
+	err := filepath.Walk(".", markFn)
+	if err != nil {
+		log.Fatal(err)
+	}
+	// ENDWALK OMIT
+}
+
 func initializationFunction(c chan int) {
 	c <- 1
 }