Why channels of channels of channels can be useful? Why we often see statements like make(chan chan chan int) in Go code ?
Let's look at example here or scala version
Why type of listenc is Channel[Channel[Channel[Message]]] ?
The answer is - exchanging information between goroutines in dynamic ways, like an emulation of asynchronous method calls between objects.
Let we want to request information which must return to us some 'A'.
Instead calling o.f(x) and invocation of a method which will return A on the stack, we create a channel
(of type Channel[A]) and pass one to target goroutine via endpoint channel (which will have type Channel[Channel[A]]).
After this goroutine will retrieve a and send one back to the canal which was received from the endpoint.
So, if we see in signature Channel[Channel[A]] this usually means "entry for information request about 'A'".