What behavior is expected if you try to close a channel that has already been closed earlier?

In Go, attempting to close an already closed channel results in a panic.

A channel can only be closed once to signal that no more values will be sent.

If close(ch) is called again on the same channel, the program will crash with an error.

Example:

ch := make(chan int)
close(ch)       // correct
close(ch)       // panic: close of closed channel

Therefore, it is important to ensure that the channel is closed only once.