Go buffer channel (bufchan) usage

Unbuffered channel:

 make(chan T)
一次发送 一次接收 都是阻塞的

Buffer channel:

 make(chan T, capacity)
发送：缓冲区数据满了才阻塞
接收：缓冲区数据空了才接收

---

for example:

 package main

import (
    "fmt"
    "strconv"
)

func main() {
    //非缓冲通道
    ch1 := make(chan int)
    fmt.Println(len(ch1), cap(ch1)) //0 0

    //缓存通道
    ch2 := make(chan int, 5)
    ch2 <- 100
    ch2 <- 200
    ch2 <- 300
    ch2 <- 400
    ch2 <- 500
    fmt.Println(len(ch2), cap(ch2))
    fmt.Println("=======================")
    ch3 := make(chan string, 4)
    //    启动一个子协程 放进去ch3
    go sendData(ch3)
    for {
        v, ok := <-ch3
        if !ok {
            fmt.Println("Reading completed ")
            break
        }
        fmt.Println("\tthe data read is : ", v)
    }
    fmt.Println("main-goroutine is finished")
}

func sendData(ch chan string) {
    for i := 0; i < 10; i++ {
        ch <- "Data " + strconv.Itoa(i)
        fmt.Println("子协程写入第 %d 个数据", i)
    }
    close(ch)
}

The result of running is:

 0 0
5 5
=======================
子协程写入第 %d 个数据 0
子协程写入第 %d 个数据 1
子协程写入第 %d 个数据 2
子协程写入第 %d 个数据 3
子协程写入第 %d 个数据 4
        the data read is :  Data 0
        the data read is :  Data 1
        the data read is :  Data 2
        the data read is :  Data 3
        the data read is :  Data 4
        the data read is :  Data 5
子协程写入第 %d 个数据 5
子协程写入第 %d 个数据 6
子协程写入第 %d 个数据 7
子协程写入第 %d 个数据 8
子协程写入第 %d 个数据 9
        the data read is :  Data 6
        the data read is :  Data 7
        the data read is :  Data 8
        the data read is :  Data 9
Reading completed 
main-goroutine is finished

In fact, it is caused by the buffer size we set to 4.

Reference: bilibili