Add context with timeout to darwin Read() calls (#674)

* Add timeout

* Clean

pkg/avfoundation/avfoundation_darwin.go

@@ -136,11 +136,26 @@ func (rc *ReadCloser) dataCb(data []byte) {
 //   - For video, each call will return a frame.
 //   - For audio, each call will return a chunk which its size configured by Latency
 func (rc *ReadCloser) Read() ([]byte, func(), error) {
-	data, ok := <-rc.dataChan
-	if !ok {
-		return nil, func() {}, io.EOF
+	data, release, err := rc.ReadContext(context.Background())
+	if err != nil {
+		return nil, release, err
+	}
+	return data, release, nil
+}
+
+// ReadContext is Read but with a context for better error handling e.g. timeout, cancellation, etc.
+func (rc *ReadCloser) ReadContext(ctx context.Context) ([]byte, func(), error) {
+	release := func() {} // no-op to satisfy Reader interface
+
+	select {
+	case <-ctx.Done():
+		return nil, release, ctx.Err()
+	case data, ok := <-rc.dataChan:
+		if !ok {
+			return nil, release, io.EOF
+		}
+		return data, release, nil
 	}
-	return data, func() {}, nil
 }
 
 // Close closes the capturing session, and no data will flow anymore

pkg/driver/camera/camera_darwin.go

@@ -1,7 +1,11 @@
 package camera
 
 import (
+	"context"
+	"errors"
 	"image"
+	"io"
+	"time"
 
 	"github.com/pion/mediadevices/pkg/avfoundation"
 	"github.com/pion/mediadevices/pkg/driver"
@@ -14,8 +18,11 @@ type camera struct {
 	device  avfoundation.Device
 	session *avfoundation.Session
 	rcClose func()
+	cancel  context.CancelFunc
 }
 
+const readTimeout = 3 * time.Second
+
 func init() {
 	Initialize()
 }
@@ -53,6 +60,11 @@ func (cam *camera) Close() error {
 	if cam.rcClose != nil {
 		cam.rcClose()
 	}
+
+	if cam.cancel != nil {
+		cam.cancel()
+	}
+
 	return cam.session.Close()
 }
 
@@ -66,10 +78,24 @@ func (cam *camera) VideoRecord(property prop.Media) (video.Reader, error) {
 	if err != nil {
 		return nil, err
 	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cam.cancel = cancel
 	cam.rcClose = rc.Close
 	r := video.ReaderFunc(func() (image.Image, func(), error) {
-		frame, _, err := rc.Read()
+		if ctx.Err() != nil {
+			// Return EOF if the camera is already closed.
+			return nil, func() {}, io.EOF
+		}
+
+		readCtx, cancel := context.WithTimeout(ctx, readTimeout)
+		defer cancel()
+
+		frame, _, err := rc.ReadContext(readCtx)
 		if err != nil {
+			if errors.Is(err, context.DeadlineExceeded) || errors.Is(err, context.Canceled) {
+				return nil, func() {}, io.EOF
+			}
 			return nil, func() {}, err
 		}
 		return decoder.Decode(frame, property.Width, property.Height)