Golang Context.Err方法代碼示例

// Send sends push notification to the APNs.
func (c *PersistentClient) Send(ctx context.Context, pn *PushNotification) *PushNotificationResponse {

	resp := NewPushNotificationResponse(pn)
	payload, err := pn.ToBytes()
	if err != nil {
		resp.Success = false
		resp.Error = err
		return resp
	}

	_, err = c.Write(payload)
	if err != nil {
		resp.Success = false
		resp.ResponseCommand = LocalResponseCommand
		resp.ResponseStatus = RetryPushNotificationStatus
		resp.Error = err
		return resp
	}
	log.Println("Sending push notification with ID", pn.Identifier)

	// This channel will contain the raw response
	// from Apple in the event of a failure.
	responseChannel := make(chan []byte, 1)
	go func() {
		buffer := make([]byte, 6)
		n, err := c.Read(buffer)
		if n != 6 && err != nil {
			buffer[0] = LocalResponseCommand
			e, ok := err.(net.Error)
			switch {
			case err == io.EOF: // Socket has been closed
				buffer[1] = RetryPushNotificationStatus
			case ok && e.Timeout(): // There is an error and it is a timeout
				buffer[1] = NoErrorsStatus
			default:
				buffer[1] = UnknownErrorStatus
			}
		}
		responseChannel <- buffer
	}()

	select {
	case <-ctx.Done():
		<-responseChannel // Wait for the read to end.
		resp.Success = false
		resp.ResponseCommand = LocalResponseCommand
		resp.ResponseStatus = CanceledPushNotificationStatus
		resp.Error = ctx.Err()
	case r := <-responseChannel:
		resp.FromRawAppleResponse(r)
	}
	return resp
}

// httpDo issues the HTTP request and calls f with the response. If ctx.Done is
// closed while the request or f is running, httpDo cancels the request, waits
// for f to exit, and returns ctx.Err. Otherwise, httpDo returns f's error.
func httpDo(ctx context.Context, req *http.Request, f func(*http.Response, error) error) error {
	// Run the HTTP request in a goroutine and pass the response to f.
	tr := &http.Transport{}
	client := &http.Client{Transport: tr}
	c := make(chan error, 1)
	go func() { c <- f(client.Do(req)) }()
	select {
	case <-ctx.Done():
		tr.CancelRequest(req)
		<-c // Wait for f to return.
		return ctx.Err()
	case err := <-c:
		return err
	}
}

// Call sends the request, waits for it to complete, and returns its error status.
func (client *Client) Call(ctx context.Context, req proto.Message, resp proto.Message) error {
	// Setup a new call
	call := &Call{
		Req:     req,
		Resp:    resp,
		cancelc: make(chan interface{}),
	}

	// Make sure a service name is passed
	if serviceName, ok := ServiceNameFromContext(ctx); !ok {
		return ErrServiceNameMissing
	} else {
		call.Service = serviceName
	}

	// If a manual deadline is not passed, setup with default timeout
	if _, ok := ctx.Deadline(); !ok {
		ctx, _ = context.WithDeadline(ctx, time.Now().Add(RequestTimeout))
	}

	// Run the request in a goroutine and write the reponse to c
	c := make(chan error, 1)
	go func() { c <- client.send(ctx, call) }()
	select {
	// Use context done to manually trigger cancel
	case <-ctx.Done():
		// Cancel the request in flight
		call.cancelc <- true
		<-c // Wait for the request to finish
		if ctx.Err() == context.DeadlineExceeded {
			return ErrTimeout
		}
		return ctx.Err()
	// Request finished
	case err := <-c:
		return err
	}
}