rchan

ResponseChan, a simple method to get a uint64 value for a channel that can be used to receive a later response.

This can be used alongside time.Time to send requests to an async peer and connect responses back.

usage

On one side:

	id, ch := rchan.New()
	defer id.Release() // it is important to release the id after use
	sendRequest(id, ...) // will send the request via rpc/etc, response is expected to come back through a different channel

	select {
	case res := <-ch:
		// got a response!
		return res, nil
	case <-ctx.Done():
		// expired
		return nil, ctx.Err()
	}

And another side receiving the response from the IPC/etc:

	id := rchan.Id(response.id)
	id.SendTimeout(100*time.Millisecond, response.data) // this will safely send the response to the recipient, other methods are also available

Note that the sending side should always have a timeout in order to avoid deadlocks from a race condition happening between the time when read times out and the channel is released. Go's chan structure provides no good way to deal with this, as for example closing the channel will cause writes to panic without providing a way to avoid this with a success check such as with reads.

This could be avoided by using a more complex structure but the goal of this library is to provide the lightest possible way to use go channels. This race condition case is unlikely enough so that a timeout will be good enough.

API

Functions

• New() (Id, <-chan any) - Creates a new response channel and returns its Id along with the receive-only channel.

Type Id

Id is a uint64 identifier for a response channel. An Id of 0 is reserved and never returned by New, allowing it to signal "no response expected".

Methods

• Release() - Releases the channel from the internal map. Must be called when done waiting (use defer).
• C() chan<- any - Returns the send-only channel associated with this Id, or nil if released/invalid.
• Send(ctx context.Context, v any) error - Sends a value to the channel, respecting context cancellation.
• SendTimeout(max time.Duration, v any) error - Sends a value with a timeout instead of a context.

Errors

• ErrChanClosed - Returned when sending to a released or invalid Id.