Resend the same value to several places without handling subscribers. (Not recommended for production.)

tunnel.go

type Tunnel[T any] struct {
	ch chan T
}

func (t *Tunnel[T]) Send(ctx context.Context, value T) error {
	select {
	case t.ch <- value:
		return nil
	case <-ctx.Done():
		return ctx.Err()
	}
}

func (t *Tunnel[T]) Recv(ctx context.Context) (T, error) {
	select {
	case value := <-t.ch:
		go func() {
			t.ch <- value
		}()

		return value, nil
	case <-ctx.Done():
		var zero T

		return zero, ctx.Err()
	}
}