Waiting for Threads

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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
}