Implement CancelWatchConfig which allows one to turn off the watcher

README.md

@@ -123,6 +123,9 @@ viper.OnConfigChange(func(e fsnotify.Event) {
 })
 ```
 
+If you wish to stop watching the configPaths, simply call viper.CancelWatchConfig().
+Note: This might be necessary if your tests involve trying out various config files.
+
 ### Reading Config from io.Reader
 
 Viper predefines many configuration sources such as files, environment

viper.go

@@ -202,6 +202,7 @@ type Viper struct {
 	properties *properties.Properties
 
 	onConfigChange func(fsnotify.Event)
+	watchConfigCancel func() (waiter func())
 }
 
 // New returns an initialized Viper instance.
@@ -300,6 +301,13 @@ func (v *Viper) WatchConfig() {
 
 		eventsWG := sync.WaitGroup{}
 		eventsWG.Add(1)
+		v.watchConfigCancel = func() (waiter func()) {
+			watcher.Close()
+			v.watchConfigCancel = nil
+			return func() {
+				eventsWG.Wait()
+			}
+		}
 		go func() {
 			for {
 				select {
@@ -346,6 +354,16 @@ func (v *Viper) WatchConfig() {
 	initWG.Wait() // make sure that the go routine above fully ended before returning
 }
 
+func CancelWatchConfig() (future func()) {
+	return v.CancelWatchConfig()
+}
+func (v *Viper) CancelWatchConfig() (future func()) {
+	if v.watchConfigCancel != nil {
+		return v.watchConfigCancel()
+	}
+	return func(){}
+}
+
 // SetConfigFile explicitly defines the path, name and extension of the config file.
 // Viper will use this and not check any of the config paths.
 func SetConfigFile(in string) { v.SetConfigFile(in) }

viper_test.go

@@ -1510,6 +1510,44 @@ func TestWatchFile(t *testing.T) {
 		assert.Equal(t, "baz", v.Get("foo"))
 	})
 
+	t.Run("file content changed after cancel", func(t *testing.T) {
+		// given a `config.yaml` file being watched
+		v, configFile, cleanup := newViperWithConfigFile(t)
+		defer cleanup()
+		_, err := os.Stat(configFile)
+		require.NoError(t, err)
+		t.Logf("test config file: %s\n", configFile)
+
+		// first run through with watching enabled
+		wg := sync.WaitGroup{}
+		wg.Add(1)
+		v.OnConfigChange(func(in fsnotify.Event) {
+			t.Logf("WatchConfig saw first config change")
+			wg.Done()
+		})
+		v.WatchConfig()
+		// when overwriting the file and waiting for the custom change notification handler to be triggered
+		err = ioutil.WriteFile(configFile, []byte("foo: baz\n"), 0640)
+		wg.Wait()
+		// then the config value should have changed
+		require.Nil(t, err)
+		assert.Equal(t, "baz", v.Get("foo"))
+
+		// cancel and wait for the canceling to finish.
+		waitForCancel := v.CancelWatchConfig()
+		v.OnConfigChange(func(in fsnotify.Event) {
+			t.Error("CancelWatchConfig did not prevent second change from being seen.")
+		})
+		waitForCancel()
+
+		err = ioutil.WriteFile(configFile, []byte("foo: quz\n"), 0640)
+		// We need to sleep a bit here because there isn't any signal of use for this invisible write.
+		time.Sleep(30 * time.Millisecond)
+
+		// the config value should still be the same.
+		require.Nil(t, err)
+		assert.Equal(t, "baz", v.Get("foo"), "CancelWatchConfig did not prevent second change from being seen.")
+	})
 }
 
 func BenchmarkGetBool(b *testing.B) {