cluster: race condition in raft/cluster

[SUMUKHA-PK]

Describe the bug
The raft/cluster package has a message queue channel which passes on the incoming messages through it like this:

c.messages <- incomingPayload{
			origin:  conn,
			payload: data,
		}

This channel when closed asynchronously from its parent function leads to a race condition.

To Reproduce
Reproduced while cluster.Close() is called, in the raft branch.

Expected behavior
Race conditions must not exist, ever!

Screenshots

[SUMUKHA-PK]

Solved using a select in the sending phase. Check for a close signal and close if that exists, else send the messages.