I am trying my hands on goroutines and came up this example - https://go.dev/play/p/mWHUmALk-1_K
But I am having this error - fatal error: all goroutines are asleep - deadlock!
I have tried to fix this but no luck. Please how do I fix this?
The error seem to be on lines 15, 23 and 32.
CodePudding user response：
The problem is that your program starts 3 separate goroutines that send to the same channel. And you have only the main goroutine receive from that channel only once. This causes the second channel send (ch <- fmt.Sprintf("...) to block indefinitely. With unbuffered channels you need to do as many receives as you do sends.
One approach to ensure all sends are received would be to use a range loop over the channel.
func getLength(dd []string, wg *sync.WaitGroup) {
wg.Add(len(dd))
c := make(chan string)
for _, d := range dd {
d1 := d
go computeLength(d1, c, wg)
}
// close c once all goroutines are done to
// ensure the for-range loop below exits.
go func() { wg.Wait(); close(c) }()
// Use for-range loop on the channel to receive all the sends.
//
// But note that a for-range loop over a channel exits only
// when the channel is closed or the loop is exited from within.
//
// So to exit you can close c once wg.Wait() returns,
// that's why there's that extra goroutine above.
for v := range c {
fmt.Println(v)
}
}