go - 发送 channel 后Goroutine无法执行

Question

package main

import (
    "fmt"
    "sync"
)

// PUT function
func put(hashMap map[string](chan int), key string, value int, wg *sync.WaitGroup) {
    defer wg.Done()
    fmt.Printf("this is getting printed")
    hashMap[key] <- value
    fmt.Printf("this is not getting printed")
    fmt.Printf("PUT sent %d\n", value)
}

func main() {
    var value int
    var key string
    wg := &sync.WaitGroup{}
    hashMap := make(map[string](chan int), 100)
    key = "xyz"
    value = 100
    for i := 0; i < 5; i++ {
        wg.Add(1)
        go put(hashMap, key, value, wg)
    }
    wg.Wait()
}

put函数中的最后两个print语句未得到打印，我正在尝试根据键将值放入映射中。

以及在这种情况下如何关闭hashMap。

Answer 1

您需要创建一个 channel ，例如hashMap[key] = make(chan int)

由于您不是从 channel 中读取内容，因此需要缓冲 channel 才能使其正常工作:

    key := "xyz"
    hashMap[key] = make(chan int, 5)

尝试以下代码:

func put(hashMap map[string](chan int), key string, value int, wg *sync.WaitGroup) {
    hashMap[key] <- value
    fmt.Printf("PUT sent %d\n", value)
    wg.Done()
}
func main() {
    var wg sync.WaitGroup
    hashMap := map[string]chan int{}
    key := "xyz"
    hashMap[key] = make(chan int, 5)
    for i := 0; i < 5; i++ {
        wg.Add(1)
        go put(hashMap, key, 100, &wg)
    }
    wg.Wait()
}

输出:

PUT sent 100
PUT sent 100
PUT sent 100
PUT sent 100
PUT sent 100