golang 中内存模型

https://segmentfault.com/a/1190000008230146

package main

import (
  "time"
  "log"
)

var a string

func hello() {
  time.Sleep(time.Millisecond * 900) // 这里如果sleep 1 秒的话， 执行程序时可能看不到打印的 “hello”
  log.Println(a)
}

func main() {
  a = "hello
"
  go hello()
  time.Sleep(time.Second)
}

　　

package main

import (
//  "log"
  "time"
)

var a string
var c = make(chan int)
func main() {
  go func() { 
    a = "hello
"
  print("recv begin..
")
  time.Sleep(time.Second*3)
  <-c
  sum :=0                        //后面这四行注释，打印顺序变为：sb, rb, re,se.  不注释时打印顺序可能为：sb,rb,re,se. (sb: send begin, se: send end..)
  for i := 0; i<1<<24; i++ {
    sum += i
  }
  print("recv end..
")
  }()
    print("send begin..
")
    c <-12
    print("send end..
")
  print(a)
  time.Sleep(time.Second*2)
}

                                           

　　

 注释4行：