What are the rules (axioms) for working with channels in Go?

In Go, channels are used for communication between goroutines and have several key rules (axioms):

• A channel is a typed queue that provides synchronization between sender and receiver.
• Sending to a channel blocks the goroutine if the channel buffer is full (for buffered channels) or if there is no receiver (for unbuffered channels).
• Receiving from a channel blocks the goroutine if the channel is empty.
• Closing a channel (close(ch)) signals that no more sends will occur; receiving from a closed channel returns the zero value and false as the second value.
• You cannot send to a closed channel — this will cause a panic.
• Channels can be used for data transfer and synchronization, but not for storing state.

Example:

ch := make(chan int, 1) // buffered channel
ch <- 42                // send
val := <-ch             // receive

close(ch)               // close the channel
v, ok := <-ch           // ok == false if the channel is closed and empty

These rules ensure safe and predictable interaction between goroutines via channels.