Context

context使用

func WithCancel(parent Context) (ctx Context, cancel CancelFunc)
func WithDeadline(parent Context, deadline time.Time) (Context, CancelFunc)
func WithTimeout(parent Context, timeout time.Duration) (Context, CancelFunc)
func WithValue(parent Context, key, val interface{}) Context

• context提供4种实现

传递共享数据

package main

import (
    "context"
    "fmt"
)

func main() {
    ctx := context.Background()
    process(ctx)
    ctx = context.WithValue(ctx, "traceId", "qcrao-2020")
    process(ctx)
}
func process(ctx context.Context) {
    traceId, ok := ctx.Value("traceId").(string)
    if ok {
        fmt.Printf("process over. trace_id=%s\n", traceId)
    } else {
        fmt.Printf("process over. no trace_id\n")
    }
}

定时取消

package main

import (
    "context"
    "testing"
)

func TestTimeoutContext(t *testing.T) {
    ctx, can := context.WithTimeout(context.Background(), 1*time.Second)
    defer can()
    go func() {
        for {
            select {
            case <-ctx.Done():
                t.Log("done")
                return
            default:
                t.Log("not done")
            }
        }
    }()
}