go:chan分为阻塞和非阻塞

一句话总结：ch := make(chan int) 由于没有缓冲发送和接收需要同步，ch := make(chan int, 2) 有缓冲不要求发送和接收操作同步。

1、无缓冲时，发送阻塞直到数据被接收，接收阻塞直到读到数据

package main

import (

	"fmt"

	"time"

)

func main() {

	ch := make(chan int)

	go func() {

		var sum int = 6

		fmt.Println("first send")

		ch <- sum

		fmt.Println("second send start")

		fmt.Println("second send")

		ch <- sum

	}()

	time.Sleep(1e9)

	fmt.Println("first recv")

	fmt.Println(<-ch)

	fmt.Println("second recv")

	fmt.Println(<-ch)

}

first send

first recv

6

second recv

second send start

second send

6

2、有缓冲时，当缓冲满时发送阻塞，当缓冲空时接收阻塞

package main

import (

	"fmt"

	"time"

)

func main() {

	ch := make(chan int, 2)

	go func() {

		var sum int = 6

		fmt.Println("first send")

		ch <- sum

		fmt.Println("second send start")

		time.Sleep(1e9)

		fmt.Println("second send")

		ch <- sum

		fmt.Println("third send start")

		time.Sleep(1e9)

		fmt.Println("third send")

		ch <- sum

		time.Sleep(1e9)

		fmt.Println("forth send")

		ch <- sum

	}()

	time.Sleep(6e9)

	fmt.Println("first recv")

	fmt.Println(<-ch)

	fmt.Println("second recv")

	fmt.Println(<-ch)

	fmt.Println("third recv")

	fmt.Println(<-ch)

	fmt.Println("forth recv")

	fmt.Println(<-ch)

}

first send

second send start

second send

third send start

third send

first recv

6

second recv

6

third recv

6

forth recv

forth send

6