Why deadlock happens?

[Akezhan_Esbolatov (AkezhanOb1)]

why in this case it is a dedlock on the line #23 (<- done)

package  main


func main() {
c := make(chan int)
done := make(chan bool)

go func() {
	for i := 0; i < 50; i++ {
		c <- i
	}
	done <- true
}()

go func() {
	for i := 0; i < 50; i++ {
		c <- i
	}
	done <- true
}()


<- done
<- done

close(c)

for i := range c {
	println(i)
 }
}

but in this case there is no deadlock

package  main

import "time"

func main() {
c := make(chan int)



go func() {
	for i := 0; i < 50; i++ {
		<- c
	}
}()


time.Sleep(time.Second * 5)
}

also why there is no deadlock when main thread is sleeping?

[NobbZ (Norbert Melzer)]

c is unbuffered and will not accept a second item before the first was read. As you never read from c, no loop will ever succeed to finish so there is never something sent to done.

[Akezhan_Esbolatov (AkezhanOb1)]

but in the second example, just writing but no reading from the channel but it works fine

[NobbZ (Norbert Melzer)]

Because you don’t have a done channel there that you wait for. Your main go routine just exits after 5 seconds and does not care for the status of its children.