adding Unwatch function for file provider

providers/file/file.go

@@ -15,7 +15,8 @@ import (
 
 // File implements a File provider.
 type File struct {
-	path string
+	path     string
+	watchers []*fsnotify.Watcher
 }
 
 // Provider returns a file provider.
@@ -122,7 +123,19 @@ func (f *File) Watch(cb func(event interface{}, err error)) error {
 
 		w.Close()
 	}()
-
+	f.watchers = append(f.watchers, w)
 	// Watch the directory for changes.
 	return w.Add(fDir)
 }
+
+// Unwatch stops watching the files. It closes all the fsnotify watchers
+// and event channels associated with them.
+func (f *File) Unwatch() error {
+	for _, watcher := range f.watchers {
+		err := watcher.Close()
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}

tests/koanf_test.go

@@ -476,6 +476,39 @@ func TestWatchFile(t *testing.T) {
 	}, "file watch reload didn't change config")
 }
 
+func TestUnwatchFile(t *testing.T) {
+	var (
+		assert = assert.New(t)
+		k      = koanf.New(delim)
+	)
+
+	// Create a tmp config file.
+	tmpDir := t.TempDir()
+	tmpFile := filepath.Join(tmpDir, "koanf_mock")
+	err := os.WriteFile(tmpFile, []byte(`{"parent": {"name": "name1"}}`), 0600)
+	require.NoError(t, err, "error creating temp config file: %v", err)
+
+	// Load the new config file.
+	f := file.Provider(tmpFile)
+	k.Load(f, json.Parser())
+
+	var wg sync.WaitGroup
+	wg.Add(1) // our assurance that cb is called max once
+	f.Watch(func(event interface{}, err error) {
+		expectedErrorMessage := "fsnotify watch channel closed"
+		// When the file is changed, and the fsnotify watch channel is closed, an error is thrown. Assert this condition.
+		assert.EqualError(err, expectedErrorMessage, "Expected error message: %s", expectedErrorMessage)
+		wg.Done()
+	})
+
+	// unwatch the file so that it is not reloaded when changed
+	f.Unwatch()
+	// Wait a second and change the file.
+	time.Sleep(1 * time.Second)
+	os.WriteFile(tmpFile, []byte(`{"parent": {"name": "name2"}}`), 0600)
+	wg.Wait()
+}
+
 func TestWatchFileSymlink(t *testing.T) {
 	var (
 		assert = assert.New(t)