A goroutine that prints odd and even numbers alternately gets stuck in deadlock

"The goroutine that alternately prints odd and even numbers falls into a deadlock" is a common problem in concurrent programming. When using goroutine for concurrent operations, if there is no correct synchronization mechanism, it can easily lead to deadlock. Deadlock is a state in which two or more processes (or goroutines) are unable to continue execution because they are waiting for each other to release resources. This article will introduce the cause of this problem and provide solutions to help developers better understand the deadlock problem in concurrent programming.

Question content

I am currently learning golang. I want to check how golang channels work. I created a program where two goroutines will alternately print odd and even numbers. Even though the program prints correctly, it still shows a deadlock error at the end. It's not clear from the error message what causes this problem.

func main() {
    even := make(chan bool)
    odd := make(chan bool)
    go func() {
        defer close(odd)
        for i := 0; i <= 10; i += 2 {
            <-even
            print("even ====>")
            println(i)
            odd <- true
        }
    }()
    var wait sync.waitgroup
    wait.add(1)
    go func() {
        for i := 1; i <= 10; i += 2 {
            _, ok := <-odd
            if !ok {
                wait.done()
                return
            }
            print("odd ====>")
            println(i)
            even <- true
        }
    }()
    even <- true
    wait.wait()
}

[edit] thanks for your replies. I wrote the following code to solve the problem.

func main() {
    even := make(chan bool)
    odd := make(chan bool)
    done := make(chan bool)
    //var wait sync.WaitGroup
    //wait.Add(2)
    go func() {
        for i := 0; i <= 10; i += 2 {
            <-even
            print("Even ====>")
            println(i)
            odd <- true
        }
        close(odd)
        close(even)
        done <- true
        // wait.Done()
    }()
    go func() {
        for i := 1; ; i += 2 {
            _, ok := <-odd
            if !ok {
                //wait.Done()
                return
            }
            print("Odd ====>")
            println(i)
            select {
            case even <- true:
            case <-done:
                return
            }
        }
    }()
    even <- true
    //wait.Wait()
    <-done
}

Solution

The problem can be solved in the following ways

1. Remove the for cap of the second gofunc (line 20)
2. selecting when writing even (line 28)

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