Error: Cache was not empty

[ggwpez]

I encountered the following error while implementing the payment-client. Did not see it before 😲
Any idea @RmbRT ? What does it mean?

Error:          Received unexpected error:
                cache was not empty (1)

                perun.network/go-perun/wire.(*Relay).Close
                        go-perun@710bca705353/wire/relay.go:61
                perun.network/go-perun/client.(*channelConn).Close
                        go-perun@710bca705353/client/channelconn.go:92
                perun.network/go-perun/client.(*Channel).Close
                        go-perun@710bca705353/client/channel.go:108
                github.com/perun-network/perun-eth-payment.(*Channel).close
                        perun-eth-payment/channel.go:137
                github.com/perun-network/perun-eth-payment.(*Channel).Close
                        perun-eth-payment/channel.go:124
                closing channel object
--- FAIL: TestAliceBob (2.61s)
FAIL
FAIL    github.com/perun-network/perun-eth-payment      2.629s
FAIL

PS: I was trying to close a channel on both ends.

[RmbRT]

I guess some race occurred and a message got cached that should actually have been received.

[RmbRT]

Some message got stuck in a wire.Relay. Either it was added while closing, when no listener was left, or it was never consumed.

[ggwpez]

Ok thanks. This confirms that a channel can not be closed by both parties at the same time.
Since we do not support full-duplex channels, i think this race is acceptable.