An example of using goroutine channel synchronization and communication to emulate the yield control statement from popular programming languages.

yield_example.go

/*
    Copyright © 2013 Mario (BU) Flores Rey CC BY-NC-SA 4.0 DEED
    License: https://creativecommons.org/licenses/by-nc-sa/4.0/
    Tested on GO v1.2.2
*/

package main

import (
    "fmt"
    "math/rand"
    "time"
)

func YieldInt(fn func(ch chan int)) chan int {
    ch := make(chan int)
    go fn(ch)
    return ch
}

func YieldRune(fn func(ch chan rune)) chan rune {
    ch := make(chan rune)
    go fn(ch)
    return ch
}

func YieldString(fn func(ch chan string)) chan string {
    ch := make(chan string)
    go fn(ch)
    return ch
}


func TestYieldSequentialInt() {
    var yieldInt chan int
    yieldInt = YieldInt(func(ch chan int) {
        const start int = 100
        const end int = 1000
        const step int = 50
        time.Sleep(3 * time.Second)
        for i := start; i <= end; i+=step {
            ch <- i
            time.Sleep(100 * time.Millisecond)
        }
        close(ch)
    })
    for n := range yieldInt {
        fmt.Printf("%d ", n)
    }
    fmt.Println()
}

func TestYieldRandomInt() {
    var yieldInt chan int
    yieldInt = YieldInt(func(ch chan int) {
        const count int = 10 // constant number of integers to yield
        time.Sleep(3 * time.Second)
        for i := 0; i < count; i++ {
            ch <- rand.Int()
            time.Sleep(100 * time.Millisecond)
        }
        close(ch)
    })
    for n := range yieldInt {
        fmt.Printf("%d ", n)
    }
    fmt.Println()
}

func TestYieldRune() {
    sentence := "the quick brown fox jumped over the lazy dog"
    var yieldRune chan rune
    yieldRune = YieldRune(func(ch chan rune) {
        time.Sleep(3 * time.Second)
        for _, c := range sentence {
            ch <- c
            time.Sleep(100 * time.Millisecond)
        }
        close(ch)
    })
    for c := range yieldRune {
        fmt.Printf("%c ", c)
    }
    fmt.Println()
}

func TestYieldString() {
    words := []string {
        "the",
        "quick",
        "brown",
        "fox",
        "jumped",
        "over",
        "the",
        "lazy",
        "dog",
    }
    var yieldString chan string
    yieldString = YieldString(func(ch chan string) {
        time.Sleep(3 * time.Second)
        for _, s := range words {
            ch <- s
            time.Sleep(100 * time.Millisecond)
        }
        close(ch)
    })
    for s := range yieldString {
        fmt.Printf("%s ", s)
    }
}

func main() {
    TestYieldSequentialInt()
    TestYieldRandomInt()
    TestYieldRune()
    TestYieldString()
}