Waiting for Threads

Post Example
Examples in Go
Go Select
by yhuang Go fmt.Println time.Second time.Sleep fmt time
Go’s select lets you wait on multiple channel operations. Combining goroutines and channels with select is a powerful feature of Go.
package main

import (
    "fmt"
    "time"
)

func main() {

    c1 := make(chan string)
    c2 := make(chan string)

    go func() {
        time.Sleep(1 * time.Second)
        c1 <- "one"
    }()
    go func() {
        time.Sleep(2 * time.Second)
        c2 <- "two"
    }()

    for i := 0; i < 2; i++ {
        select {
        case msg1 := <-c1:
            fmt.Println("received", msg1)
        case msg2 := <-c2:
            fmt.Println("received", msg2)
        }
    }
}
Go WaitGroup
by yhuang Go fmt.Printf sync.WaitGroup fmt sync sync.WaitGroup.Add
To wait for multiple goroutines to finish, we can use a wait group.
package main

import (
    "fmt"
    "sync"
    "time"
)

func worker(id int, wg *sync.WaitGroup) {
    fmt.Printf("Worker %d starting\n", id)

    time.Sleep(time.Second)
    fmt.Printf("Worker %d done\n", id)

    wg.Done()
}

func main() {

    var wg sync.WaitGroup

    for i := 1; i <= 5; i++ {
        wg.Add(1)
        go worker(i, &wg)
    }

    wg.Wait()
}
Waiting for threads using Go channels.
by yhuang Go fmt fmt.Print fmt.Println time time.Second
We can use channels to synchronize execution across goroutines. Here’s an example of using a blocking receive to wait for a goroutine to finish.
package main

import (
    "fmt"
    "time"
)

func worker(done chan bool) {
    fmt.Print("working...")
    time.Sleep(time.Second)
    fmt.Println("done")

    done <- true
}

func main() {

    done := make(chan bool, 1)
    go worker(done)

    <-done
}