Give the complete table of channel operation behavior for nil, open, and closed channels.

Operation	nil channel	open channel	closed channel
send ch <- v	blocks forever	blocks until received/buffer space	panic
receive <-ch	blocks forever	blocks until value	drains buffer, then zero value, ok=false
close(ch)	panic	succeeds	panic
len/cap	0	queued / capacity	remaining queued / capacity

What the interviewer is looking for: you should know all three panics (send on closed, close of nil, double close) and understand that "blocks forever" on nil is a feature that select uses to turn cases off dynamically. Candidates often say that receiving from a closed channel panics. It does not. It returns buffered values first and then zero values forever.