Sharing memory
One of the most famous Go idioms is: “Do not communicate by sharing memory, share memory by communicating.” Channels are for sharing memory by communicating. Communicating by sharing memory is done using shared variables in multiple goroutines. Even though it is discouraged, there are many use cases where shared memory makes more sense than a channel. If at least one of the goroutines updates a shared variable that is read by other goroutines, you have to ensure that there are no memory races.
A memory race happens when a goroutine updates a variable concurrently while another goroutine reads from it or writes to it. When this happens, there is no guarantee that the update to that variable will be seen by other goroutines. A famous example of this situation is the busy-wait loop:
func main() {
done:=false
go func() {
// Wait while done==false
for !done {}
...
