检测goroutine是否已在运行

package main

import (
    "fmt"
    "sync"
)

func worker(done chan bool, wg *sync.WaitGroup) {
    defer wg.Done()
    fmt.Println("working...")
    done <- true
}

func main() {
    var wg sync.WaitGroup
    done := make(chan bool)

    wg.Add(1)
    go worker(done, &wg)

    // 检测goroutine是否已在运行
    select {
    case <-done:
        fmt.Println("worker has finished")
    default:
        fmt.Println("worker is running")
    }

    wg.Wait()
}

package main

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

var (
    mu    sync.Mutex
    ready bool
)

func worker(wg *sync.WaitGroup) {
    defer wg.Done()
    mu.Lock()
    ready = true
    mu.Unlock()

    fmt.Println("working...")
    time.Sleep(time.Second)
}

func main() {
    var wg sync.WaitGroup

    wg.Add(1)
    go worker(&wg)

    mu.Lock()
    if ready {
        fmt.Println("worker is running")
    } else {
        fmt.Println("worker has not started yet")
    }
    mu.Unlock()

    wg.Wait()
}