context

数据传递

package main

import (
  "context"
  "fmt"
)

func main() {
  ctx := context.Background()
  ctx = context.WithValue(ctx, "name", "张三")
  GetUser(ctx)
}

func GetUser(ctx context.Context) {
  fmt.Println(ctx.Value("name")) // 张三
}

取消协程

package main

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

var wait = sync.WaitGroup{}

func main() {
  t1 := time.Now()

  ctx, cancel := context.WithCancel(context.Background())

  wait.Add(1)
  go func() {
    ip, err := GetIP(ctx)
    if err != nil {
      fmt.Println(err)
    }
    fmt.Println(ip)
  }()

  go func() {
    time.Sleep(2 * time.Second)
    // 取消协程
    cancel()
  }()

  wait.Wait()
  fmt.Println("执行完成，耗时：", time.Since(t1))
}

func GetIP(ctx context.Context) (ip string, err error) {
  go func() {
    select {
    case <-ctx.Done():
      fmt.Println("协程取消", ctx.Err())
      err = ctx.Err()
      wait.Done()
      return
    }
  }()

  time.Sleep(4 * time.Second)
  ip = "127.0.0.1"
  wait.Done()
  return
}

截至时间

package main

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

func main() {
  var wg = sync.WaitGroup{}

  t1 := time.Now()

  ctx, _ := context.WithDeadline(context.Background(), time.Now().Add(2*time.Second))

  wg.Add(1)
  go func() {
    ip, err := GetIP(ctx, &wg)
    if err != nil {
      fmt.Println(err)
    }
    fmt.Println(ip)
  }()

  wg.Wait()
  fmt.Println("执行完成，耗时：", time.Since(t1))
}

func GetIP(ctx context.Context, wg *sync.WaitGroup) (ip string, err error) {
  go func() {
    select {
    case <-ctx.Done():
      fmt.Println("协程取消", ctx.Err())
      err = ctx.Err()
      wg.Done()
      return
    }
  }()

  time.Sleep(4 * time.Second)
  ip = "127.0.0.1"
  wg.Done()
  return
}

超时时间

package main

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

func main() {
  var wg = sync.WaitGroup{}

  t1 := time.Now()

  ctx, _ := context.WithTimeout(context.Background(), 2*time.Second)

  wg.Add(1)
  go func() {
    ip, err := GetIP(ctx, &wg)
    if err != nil {
      fmt.Println(err)
    }
    fmt.Println(ip)
  }()

  wg.Wait()
  fmt.Println("执行完成，耗时：", time.Since(t1))
}

func GetIP(ctx context.Context, wg *sync.WaitGroup) (ip string, err error) {
  go func() {
    select {
    case <-ctx.Done():
      fmt.Println("协程取消", ctx.Err())
      err = ctx.Err()
      wg.Done()
      return
    }
  }()

  time.Sleep(4 * time.Second)
  ip = "127.0.0.1"
  wg.Done()
  return
}