致命错误：所有goroutines都处于Hibernate状态-死锁

Question

package main

import (
    "fmt"
    "math/rand"
)

const (
    ROCK int = iota
    PAPER
    SCISSORS
)

type Choice struct {
    Who   int //0 you 1 your opponent
    Guess int
}

//Win returns true if you win.
func Win(you, he int) bool {
    ...
}

func Opponent(guess chan Choice, please chan struct{}) {
    for i := 0; i < 3; i++ {
        <-please
        choice := rand.Intn(3)
        who := 1
        guess <- Choice{who, choice}
        please <- struct{}{}
    }
}

func GetChoice(you, he int) int {
    ...
}

var Cheat func(guess chan Choice) chan Choice = func(guess chan Choice) chan Choice {
    new_guess := make(chan Choice)
    // go func() {
    for i := 0; i < 3; i++ {
        g1 := <-guess
        g2 := <-guess
        if g1.Who == 0 {
            choice := GetChoice(g1.Guess, g2.Guess)
            new_guess <- g2
            new_guess <- Choice{g1.Who, choice}
        } else {
            choice := GetChoice(g2.Guess, g1.Guess)
            new_guess <- g1
            new_guess <- Choice{g2.Who, choice}
        }
    }
    // }()
    fmt.Println("...")
    return new_guess
}

func Me(guess chan Choice, please chan struct{}) {

    for i := 0; i < 3; i++ {
        <-please
        choice := rand.Intn(3)
        who := 0
        guess <- Choice{who, choice}
        please <- struct{}{}
    }
}

func Game() []bool {
    guess := make(chan Choice)
    //please sync 2 goroutines.
    please := make(chan struct{})
    go func() { please <- struct{}{} }()
    go Opponent(guess, please)
    go Me(guess, please)
    guess = Cheat(guess)
    var wins []bool

    for i := 0; i < 3; i++ {
        g1 := <-guess
        g2 := <-guess
        win := false
        if g1.Who == 0 {
            win = Win(g1.Guess, g2.Guess)
        } else {
            win = Win(g2.Guess, g1.Guess)
        }
        wins = append(wins, win)
    }

    return wins
}

func main() {
    win := Game()
    fmt.Println(win)
}

Answer 1

在这个简化的示例中：

func Cheat(guess chan Choice) chan Choice {
        new_guess := make(chan Choice)
        new_guess <- Choice{}
        <-guess
        return new_guess
}

当对新分配的通道进行写操作时，没有其他人可能还拥有该通道，因此写操作将永远阻塞。由于写块，从guess读取就不会发生。但是，在您引用的代码中，cheak()函数是从gues通道读取的唯一内容；因此，写到它的内容在读发生时被阻止，在写到new_guess发生之前，读不会发生，在包含函数返回之前，写不会发生。

如果您将通道I/O移到goroutine，那么包含函数可以在事情进展之前返回，因此在cheak()中的write与game()末尾的reads配对，事情可以向前推进。