channel有缓冲与无缓冲同步问题

package main

import (
   "fmt"
   "time"
)

func main() {
   c := make(chan int, 3) //带有缓冲的channel

   fmt.Println("len(c) = ", len(c), ", cap(c)", cap(c))

   go func() {
      defer fmt.Println("子go程结束")

      for i := 0; i < 4; i++ {
         c <- i
         fmt.Println("子go程正在运行, 发送的元素=", i, " len(c)=", len(c), ", cap(c)=", cap(c))
      }
   }()
   time.Sleep(2 * time.Second)
   for i := 0; i < 4; i++ {
      num := <-c //从c中接收数据，并赋值给num
      fmt.Println("num = ", num)
   }
   fmt.Println("main 结束")
}

关闭channel

package main

import "fmt"

func main() {
   c := make(chan int)

   go func() {
      for i := 0; i < 5; i++ {
         c <- i
         //close可以关闭一个channel
         close(c)
      }
   }()
   
   for {
      //ok如果为true表示channel没有关闭，如果为false表示channel已经关闭
      if data, ok := <-c; ok {
         fmt.Println(data)
      } else {
         break
      }
   }

   fmt.Println("Main Finished..")
}