为什么将for循环与select一起使用时，为什么该golang程序会挂在操场上？

Question

Consider this playground

    messages := make(chan int, 1)
    done := make(chan bool)
    go func() {
        for {
        select {
            case msg := <- messages:
                fmt.Println("receiver one", msg)
            case signal := <-done :
                fmt.Println(signal)
                return
            default:
                fmt.Println("no message received")
        } 
        }
    }()
    go func() {
        for {
        select {
            case msg := <- messages:
                fmt.Println("receiver two", msg)
            case signal := <-done :
                fmt.Println(signal)
                return
            default:
                fmt.Println("no message received")
        } 
        }
    }()
    go func() {
       for i := 0; i < 2; i++ {
           messages<-i
       }
       done<-true
       done<-true
       done<-true
    }()

    <-done

I am trying to simulate communicate from one thread to two other thread, but it seems like the above code is running fine in my local but not in playground.

Is there a trick to make the program work?

Answer 1

You should remove the default clauses from the select statements.

Since your select statement is within a for loop and the default clause prevents it from blocking, the loop has to go through a lot of cycles before any message will be received.

Looks like Playground detects it and stops the program.