Golang并发编程中Context包的使用与并发控制

package main

import (
    "context"
    "fmt"
    "time"
)

func worker(ctx context.Context, id int) {
    for {
        select {
        case <-ctx.Done(): // 接收取消信号
            fmt.Printf("Worker %d stopped\n", id)
            return
        default:
            fmt.Printf("Worker %d is working...\n", id)
            time.Sleep(time.Second)
        }
    }
}

func main() {
    ctx, cancel := context.WithCancel(context.Background()) // 创建可取消的上下文

    for i := 1; i <= 3; i++ {
        go worker(ctx, i)
    }

    time.Sleep(3 * time.Second) // 模拟主 Goroutine 的其他工作
    fmt.Println("Cancelling all workers...")
    cancel() // 发送取消信号

    time.Sleep(1 * time.Second) // 等待所有 Goroutine 退出
    fmt.Println("All workers stopped.")
}

package main

import (
    "context"
    "fmt"
    "time"
)

func worker(ctx context.Context) {
    select {
    case <-time.After(3 * time.Second): // 模拟长时间任务
        fmt.Println("Task completed")
    case <-ctx.Done(): // 接收超时信号
        fmt.Println("Task timed out")
    }
}

func main() {
    ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second) // 设置 2 秒超时
    defer cancel() // 确保资源释放

    go worker(ctx)

    time.Sleep(4 * time.Second) // 等待任务完成或超时
}

package main

import (
    "context"
    "fmt"
    "time"
)

func greetUser(ctx context.Context) {
    if user, ok := ctx.Value("user").(string); ok {
        fmt.Printf("Hello, %s!\n", user)
    } else {
        fmt.Println("No user found.")
    }
}

func main() {
    ctx := context.WithValue(context.Background(), "user", "Alice") // 在上下文中存入用户信息
    go greetUser(ctx)

    time.Sleep(1 * time.Second) // 确保 Goroutine 执行完毕
}

package main

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

func worker(ctx context.Context, id int, wg *sync.WaitGroup) {
    defer wg.Done()

    for {
        select {
        case <-ctx.Done():
            fmt.Printf("Worker %d stopped\n", id)
            return
        default:
            fmt.Printf("Worker %d is processing...\n", id)
            time.Sleep(500 * time.Millisecond)
        }
    }
}

func main() {
    var wg sync.WaitGroup
    ctx, cancel := context.WithCancel(context.Background()) // 创建上下文

    for i := 1; i <= 3; i++ {
        wg.Add(1)
        go worker(ctx, i, &wg)
    }

    time.Sleep(2 * time.Second)
    fmt.Println("Cancelling all workers...")
    cancel() // 取消所有任务

    wg.Wait() // 等待所有任务完成
    fmt.Println("All workers stopped.")
}