【练习】goroutine chan 通道 总结

1、

fatal error: all goroutines are asleep - deadlock!

所有的协程都休眠了 - 死锁！

package main
import("fmt")
func f1(in chan int){
fmt.Println(<-in)
}
func main(){
out :=make(chan int)
out<-2
go f1(out)
}

package main
import("fmt")
func f1(in chan int){
fmt.Println(<-in)
}
func main(){
out :=make(chan int)
// out<-2
go f1(out)
out<-2
}

Understanding the context package in golang - Parikshit Agnihotry http://p.agnihotry.com/post/understanding_the_context_package_in_golang/

  package main

  import "fmt"

  //prints to stdout and puts an int on channel
  func printHello(ch chan int) {
    fmt.Println("Hello from printHello")
    //send a value on channel
    ch <- 2
  }

  func main() {
    //make a channel. You need to use the make function to create channels.
    //channels can also be buffered where you can specify size. eg: ch := make(chan int, 2)
    //that is out of the scope of this post.
    ch := make(chan int)
    //inline goroutine. Define a function and then call it.
    //write on a channel when done
    go func(){
      fmt.Println("Hello inline")
      //send a value on channel
      ch <- 1
    }()
    //call a function as goroutine
    go printHello(ch)
    fmt.Println("Hello from main")

    //get first value from channel.
    //and assign to a variable to use this value later
    //here that is to print it
    i := <- ch
    fmt.Println("Recieved ",i)
    //get the second value from channel
    //do not assign it to a variable because we dont want to use that
    <- ch
  }

　　

Hello from main
Hello from printHello
Recieved 2
Hello inline

golang channel 使用总结 - litang.me http://litang.me/post/golang-channel/

• http://www.usingcsp.com/
• https://go101.org/article/channel.html
• https://go101.org/article/channel-use-cases.html
• https://go101.org/article/channel-closing.html
• https://www.jianshu.com/p/819aa9b9af86

package main

import (
   "fmt"
   "time"
)

func fA(ch chan bool) {
   defer func() {
      fmt.Println("fA-defer")
   }()
   fmt.Println("fA-doing")
   ch <- true
   time.Sleep(time.Duration(123) * time.Millisecond)
   
}

func fB(ch chan bool) {
   defer func() {
      fmt.Println("fB-defer")
   }()
   fmt.Println("fB-doing")
   ch <- true
   
}

func main() {
   defer func() {
      fmt.Println("main-defer")
   }()
   ch := make(chan bool)
   go fA(ch)
   go fB(ch)
   <-ch
   <-ch
}

目前打印结果为：
fB-doing
fB-defer
fA-doing
main-defer
修改代码打印结果为：
fB-doing
fB-defer
fA-doing
fA-defer
main-defer

交换

ch <- true
time.Sleep(time.Duration(123) * time.Millisecond)

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