如何在Go中使用context实现请求熔断

package main

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

type CircuitBreaker struct {
    context    context.Context
    cancel     context.CancelFunc
    maxFail    int
    fail       int
    breaker    bool
    resetTime  time.Duration
    breakerMux sync.Mutex
}

func NewCircuitBreaker(maxFail int, resetTime time.Duration) *CircuitBreaker {
    ctx, cancel := context.WithCancel(context.Background())

    circuitBreaker := &CircuitBreaker{
        context:    ctx,
        cancel:     cancel,
        maxFail:    maxFail,
        fail:       0,
        breaker:    false,
        resetTime:  resetTime,
        breakerMux: sync.Mutex{},
    }

    return circuitBreaker
}

func (c *CircuitBreaker) Do(req func() error) error {
    select {
    case <-c.context.Done():
        return fmt.Errorf("circuit breaker is open")
    default:
        if !c.breaker {
            err := req()
            if err == nil {
                c.reset()
            } else {
                c.fail++
                if c.fail >= c.maxFail {
                    c.breakerMux.Lock()
                    c.breaker = true
                    c.breakerMux.Unlock()
                    go time.AfterFunc(c.resetTime, c.reset)
                }
            }
            return err
        } else {
            return fmt.Errorf("circuit breaker is open") 
        }
    }
}

func (c *CircuitBreaker) reset() {
    c.fail = 0
    c.breakerMux.Lock()
    c.breaker = false
    c.breakerMux.Unlock()
    c.cancel()
}

func main() {
    circuitBreaker := NewCircuitBreaker(3, 2*time.Minute)

    // 进行模拟请求
    for i := 0; i < 10; i++ {
        err := circuitBreaker.Do(func() error {
            // 这里执行实际的请求操作，此处只是模拟
            fmt.Println("执行请求...")
            if i%5 == 0 {
                return fmt.Errorf("request failed")
            }
            return nil
        })

        if err != nil {
            fmt.Printf("请求失败: %v
", err)
        } else {
            fmt.Println("请求成功")
        }
    }
}