How do I implement retries and circuit breakers in Go?

package main

import (
    "errors"
    "fmt"
    "time"
)

type CircuitBreaker struct {
    isOpen       bool
    failureCount int
    threshold    int
    timeout      time.Duration
    lastAttempt  time.Time
}

func NewCircuitBreaker(threshold int, timeout time.Duration) *CircuitBreaker {
    return &CircuitBreaker{
        threshold: threshold,
        timeout:   timeout,
    }
}

func (cb *CircuitBreaker) Call(do func() error) error {
    if cb.isOpen && time.Since(cb.lastAttempt) < cb.timeout {
        return errors.New("circuit is open, call failed")
    }
    
    err := do()
    if err != nil {
        cb.failureCount++
        cb.lastAttempt = time.Now()

        if cb.failureCount >= cb.threshold {
            cb.isOpen = true
            return errors.New("circuit opened due to failure")
        }
        return err
    }

    cb.failureCount = 0
    cb.isOpen = false
    return nil
}

func main() {
    cb := NewCircuitBreaker(3, 5*time.Second)

    for i := 0; i < 10; i++ {
        err := cb.Call(func() error {
            // Simulate a faulty service call:
            if time.Now().Second()%2 == 0 {
                return errors.New("simulated service failure")
            }
            fmt.Println("Service call succeeded")
            return nil
        })
        if err != nil {
            fmt.Println(err)
            time.Sleep(1 * time.Second) // Wait before retrying
        }
    }
}