Golang Context.Err方法代碼示例

func (cmd *serveEmbedCmd) run(ctx scope.Context, args []string) error {
	listener, err := net.Listen("tcp", cmd.addr)
	if err != nil {
		return err
	}

	closed := false
	m := sync.Mutex{}
	closeListener := func() {
		m.Lock()
		if !closed {
			listener.Close()
			closed = true
		}
		m.Unlock()
	}

	// Spin off goroutine to watch ctx and close listener if shutdown requested.
	go func() {
		<-ctx.Done()
		closeListener()
	}()

	if err := http.Serve(listener, cmd); err != nil {
		fmt.Printf("http[%s]: %s\n", cmd.addr, err)
		return err
	}

	closeListener()
	ctx.WaitGroup().Done()
	return ctx.Err()
}

func (jq *JobQueueBinding) WaitForJob(ctx scope.Context) error {
	ch := make(chan error)

	// background goroutine to wait on condition
	go func() {
		// synchronize with caller
		<-ch
		jq.m.Unlock()
		jq.Backend.jobQueueListener().wait(jq.Name())
		ch <- nil
	}()

	// synchronize with background goroutine
	jq.m.Lock()
	ch <- nil
	jq.m.Lock()
	jq.m.Unlock()

	select {
	case <-ctx.Done():
		jq.Backend.jobQueueListener().wakeAll(jq.Name())
		<-ch
		return ctx.Err()
	case err := <-ch:
		return err
	}
}

func Claim(ctx scope.Context, jq JobQueue, handlerID string, pollTime time.Duration, stealChance float64) (*Job, error) {
	for ctx.Err() == nil {
		if rand.Float64() < stealChance {
			job, err := jq.TrySteal(ctx, handlerID)
			if err != nil && err != ErrJobNotFound {
				return nil, err
			}
			if err == nil {
				return job, nil
			}
		}
		job, err := jq.TryClaim(ctx, handlerID)
		if err != nil {
			if err == ErrJobNotFound {
				child := ctx.ForkWithTimeout(pollTime)
				if err = jq.WaitForJob(child); err != nil && err != scope.TimedOut {
					return nil, err
				}
				continue
			}
			return nil, err
		}
		return job, nil
	}
	return nil, ctx.Err()
}

func (s *session) Send(ctx scope.Context, cmdType proto.PacketType, payload interface{}) error {
	// Special case: certain events have privileged info that may need to be stripped from them
	switch event := payload.(type) {
	case *proto.PresenceEvent:
		switch s.privilegeLevel() {
		case proto.Staff:
		case proto.Host:
			event.RealClientAddress = ""
		default:
			event.RealClientAddress = ""
			event.ClientAddress = ""
		}
	case *proto.Message:
		if s.privilegeLevel() == proto.General {
			event.Sender.ClientAddress = ""
		}
	case *proto.EditMessageEvent:
		if s.privilegeLevel() == proto.General {
			event.Sender.ClientAddress = ""
		}
	}

	var err error
	payload, err = proto.DecryptPayload(payload, &s.client.Authorization, s.privilegeLevel())
	if err != nil {
		return err
	}

	encoded, err := json.Marshal(payload)
	if err != nil {
		return err
	}

	cmd := &proto.Packet{
		Type: cmdType,
		Data: encoded,
	}

	// Add to outgoing channel. If channel is full, defer to goroutine so as not to block
	// the caller (this may result in deliveries coming out of order).
	select {
	case <-ctx.Done():
		// Session is closed, return error.
		return ctx.Err()
	case s.outgoing <- cmd:
		// Packet delivered to queue.
	default:
		// Queue is full.
		logging.Logger(s.ctx).Printf("outgoing channel full, ordering cannot be guaranteed")
		go func() { s.outgoing <- cmd }()
	}

	return nil
}

func Loop(ctx scope.Context, heim *proto.Heim, workerName, queueName string) error {
	fmt.Printf("Loop\n")
	ctrl, err := NewController(ctx, heim, workerName, queueName)
	if err != nil {
		fmt.Printf("error: %s\n", err)
		return err
	}

	ctx.WaitGroup().Add(1)
	go ctrl.background(ctx)
	ctx.WaitGroup().Wait()
	return ctx.Err()
}

func (ctrl *Controller) terminal(ctx scope.Context, ch ssh.Channel) {
	defer ch.Close()

	lines := make(chan string)
	term := terminal.NewTerminal(ch, "> ")

	go func() {
		for ctx.Err() == nil {
			line, err := term.ReadLine()
			if err != nil {
				ctx.Terminate(err)
				return
			}
			lines <- line
		}
	}()

	for {
		var line string
		select {
		case <-ctx.Done():
			return
		case line = <-lines:
		}

		cmd := parse(line)
		fmt.Printf("[control] > %v\n", cmd)
		switch cmd[0] {
		case "":
			continue
		case "quit":
			return
		case "shutdown":
			ctrl.ctx.Terminate(fmt.Errorf("shutdown initiated from console"))
		default:
			runCommand(ctx.Fork(), ctrl, cmd[0], term, cmd[1:])
		}
	}
}