Golang golang-channel (snippet)

Go programming example 'golang-channel'

golang-channel

Golang beginners example: golang-channel

package main

import (
    "fmt"
    "runtime"
    "time"
)

var chan_int chan int
var stop_bool chan bool

func init() {
    chan_int = make(chan int, 2)
    stop_bool = make(chan bool, 3)
}

func maxprocs1() {
    /*
     * Channels are useful for communications between multiple
     * go routines, even when the routines are not runned in parralel.
     *
     */

    go func() {
        time.Sleep(2 * time.Second)
        fmt.Println("1")
        stop_bool <- true
    }()
    go func() {
        time.Sleep(1900 * time.Millisecond)
        fmt.Println("2")
        stop_bool <- true
    }()
    go func() {
        time.Sleep(2 * time.Second)
        fmt.Println("3")
        stop_bool <- true
    }()

    <-stop_bool
    <-stop_bool
    <-stop_bool

    /*
     * the previous code is compareable to the following bash code:
     *
     * function1 &
     * stop1=$!
     *
     * function2 &
     * stop2=$!
     *
     * function3 &
     * stop3=$!
     *
     * wait $stop1
     * wait $stop2
     * wait $stop3
     *
     */
}

func waitforbuffer() {
    /*
     *
     * Starts a go routine which waits 2 seconds, prints the value
     * from the channel buffer and waits again (over and over again).
     * In the parrent function it tries to fill the channel with 3 integers,
     * but after the first two values it has to wait until the buffer gets
     * emptied. After 2 seconds, the first value gets loaded and printed,
     * so the next value can be saved (but will never be printed, because
     * the programm no longer have to wait for the channel and quit.
     *
     */

    go func(i int) {
        for {
            time.Sleep(time.Duration(i) * time.Second)
            fmt.Println(<-chan_int)
        }
    }(2)
    fmt.Println("start")
    chan_int <- 1
    fmt.Println("<-1")
    chan_int <- 2
    fmt.Println("<-2")
    chan_int <- 3
    fmt.Println("<-3")
}

func main() {
    runtime.GOMAXPROCS(1)
    fmt.Println("starting maxprocs1()")
    maxprocs1()
    fmt.Println("starting waitforbuffer()")
    waitforbuffer()
    fmt.Println("finish")
}

Useful links

• Learn Go: https://golangr.com
• Download Go: https://golang.org