Пример #1
0
func ExampleWithTimeout() {
	// Pass a context with a timeout to tell a blocking function that it
	// should abandon its work after the timeout elapses.
	ctx, _ := context.WithTimeout(context.Background(), 100*time.Millisecond)
	select {
	case <-time.After(200 * time.Millisecond):
		fmt.Println("overslept")
	case <-ctx.Done():
		fmt.Println(ctx.Err()) // prints "context deadline exceeded"
	}
	// Output:
	// context deadline exceeded
}
Пример #2
0
func TestCancelReadCloser(t *testing.T) {
	ctx, _ := context.WithTimeout(context.Background(), 100*time.Millisecond)
	cancelReadCloser := NewCancelReadCloser(ctx, ioutil.NopCloser(&perpetualReader{}))
	for {
		var buf [128]byte
		_, err := cancelReadCloser.Read(buf[:])
		if err == context.DeadlineExceeded {
			break
		} else if err != nil {
			t.Fatalf("got unexpected error: %v", err)
		}
	}
}
Пример #3
0
// NewCancelReadCloser creates a wrapper that closes the ReadCloser when the
// context is cancelled. The returned io.ReadCloser must be closed when it is
// no longer needed.
func NewCancelReadCloser(ctx context.Context, in io.ReadCloser) io.ReadCloser {
	pR, pW := io.Pipe()

	// Create a context used to signal when the pipe is closed
	doneCtx, cancel := context.WithCancel(context.Background())

	p := &cancelReadCloser{
		cancel: cancel,
		pR:     pR,
		pW:     pW,
	}

	go func() {
		_, err := io.Copy(pW, in)
		select {
		case <-ctx.Done():
			// If the context was closed, p.closeWithError
			// was already called. Calling it again would
			// change the error that Read returns.
		default:
			p.closeWithError(err)
		}
		in.Close()
	}()
	go func() {
		for {
			select {
			case <-ctx.Done():
				p.closeWithError(ctx.Err())
			case <-doneCtx.Done():
				return
			}
		}
	}()

	return p
}