sync/atomic: use package prefix in examples

Previously these examples declared "var v Value" but any caller would
need to write "var v atomic.Value", so we should use the external
package declaration form to avoid confusion about where Value comes
from.

Change-Id: Ic0b1a05fb6b700da61cfc8efca594c49a9bedb69
Reviewed-on: https://go-review.googlesource.com/107975Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/sync/atomic/example_test.go

+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package atomic_test
+
+import (
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+func loadConfig() map[string]string {
+	return make(map[string]string)
+}
+
+func requests() chan int {
+	return make(chan int)
+}
+
+// The following example shows how to use Value for periodic program config updates
+// and propagation of the changes to worker goroutines.
+func ExampleValue_config() {
+	var config atomic.Value // holds current server configuration
+	// Create initial config value and store into config.
+	config.Store(loadConfig())
+	go func() {
+		// Reload config every 10 seconds
+		// and update config value with the new version.
+		for {
+			time.Sleep(10 * time.Second)
+			config.Store(loadConfig())
+		}
+	}()
+	// Create worker goroutines that handle incoming requests
+	// using the latest config value.
+	for i := 0; i < 10; i++ {
+		go func() {
+			for r := range requests() {
+				c := config.Load()
+				// Handle request r using config c.
+				_, _ = r, c
+			}
+		}()
+	}
+}
+
+// The following example shows how to maintain a scalable frequently read,
+// but infrequently updated data structure using copy-on-write idiom.
+func ExampleValue_readMostly() {
+	type Map map[string]string
+	var m atomic.Value
+	m.Store(make(Map))
+	var mu sync.Mutex // used only by writers
+	// read function can be used to read the data without further synchronization
+	read := func(key string) (val string) {
+		m1 := m.Load().(Map)
+		return m1[key]
+	}
+	// insert function can be used to update the data without further synchronization
+	insert := func(key, val string) {
+		mu.Lock() // synchronize with other potential writers
+		defer mu.Unlock()
+		m1 := m.Load().(Map) // load current value of the data structure
+		m2 := make(Map)      // create a new value
+		for k, v := range m1 {
+			m2[k] = v // copy all data from the current object to the new one
+		}
+		m2[key] = val // do the update that we need
+		m.Store(m2)   // atomically replace the current object with the new one
+		// At this point all new readers start working with the new version.
+		// The old version will be garbage collected once the existing readers
+		// (if any) are done with it.
+	}
+	_, _ = read, insert
+}

src/sync/atomic/value_test.go

@@ -7,10 +7,8 @@ package atomic_test
 import (
 	"math/rand"
 	"runtime"
-	"sync"
 	. "sync/atomic"
 	"testing"
-	"time"
 )
 
 func TestValue(t *testing.T) {
@@ -133,68 +131,3 @@ func BenchmarkValueRead(b *testing.B) {
 		}
 	})
 }
-
-// The following example shows how to use Value for periodic program config updates
-// and propagation of the changes to worker goroutines.
-func ExampleValue_config() {
-	var config Value // holds current server configuration
-	// Create initial config value and store into config.
-	config.Store(loadConfig())
-	go func() {
-		// Reload config every 10 seconds
-		// and update config value with the new version.
-		for {
-			time.Sleep(10 * time.Second)
-			config.Store(loadConfig())
-		}
-	}()
-	// Create worker goroutines that handle incoming requests
-	// using the latest config value.
-	for i := 0; i < 10; i++ {
-		go func() {
-			for r := range requests() {
-				c := config.Load()
-				// Handle request r using config c.
-				_, _ = r, c
-			}
-		}()
-	}
-}
-
-func loadConfig() map[string]string {
-	return make(map[string]string)
-}
-
-func requests() chan int {
-	return make(chan int)
-}
-
-// The following example shows how to maintain a scalable frequently read,
-// but infrequently updated data structure using copy-on-write idiom.
-func ExampleValue_readMostly() {
-	type Map map[string]string
-	var m Value
-	m.Store(make(Map))
-	var mu sync.Mutex // used only by writers
-	// read function can be used to read the data without further synchronization
-	read := func(key string) (val string) {
-		m1 := m.Load().(Map)
-		return m1[key]
-	}
-	// insert function can be used to update the data without further synchronization
-	insert := func(key, val string) {
-		mu.Lock() // synchronize with other potential writers
-		defer mu.Unlock()
-		m1 := m.Load().(Map) // load current value of the data structure
-		m2 := make(Map)      // create a new value
-		for k, v := range m1 {
-			m2[k] = v // copy all data from the current object to the new one
-		}
-		m2[key] = val // do the update that we need
-		m.Store(m2)   // atomically replace the current object with the new one
-		// At this point all new readers start working with the new version.
-		// The old version will be garbage collected once the existing readers
-		// (if any) are done with it.
-	}
-	_, _ = read, insert
-}