If there is a break or panic in the iterator, not the loop using the iterator. If the loop using the iterator closes the channel, the program will crash.
The sender is supposed to close the channel to signify to the receiver that there is no more data to be sent. The receiver is not supposed to close the channel. (You could hack around this by recovering from the panic, but this is bad style.)
Note that there is no requirement that you close channels-- they aren't like file descriptors. They will be garbage collected after they're no longer needed.
goroutines, on the other hand, will stick around unless you clean them up. goroutines aren't iterators, and you shouldn't use them as iterators. They're more analogous to threads.
