What are Go and microservices architecture patterns?

Question

Accepted Answer

Microservices architecture patterns in Go.

```go
// 1. Strangler Fig: gradual migration
type Router struct {
    legacy http.Handler
    modern http.Handler
}

func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
    if r.isNewService(req.URL.Path) {
        r.modern.ServeHTTP(w, req)
    } else {
        r.legacy.ServeHTTP(w, req)
    }
}

// 2. Circuit Breaker: protect against service failures
import "github.com/sony/gobreaker"

cb := gobreaker.NewCircuitBreaker(gobreaker.Settings{
    Name:        "my-service",
    MaxRequests: 3,
    Interval:    10 * time.Second,
    Timeout:     30 * time.Second,
    ReadyToTrip: func(counts gobreaker.Counts) bool {
        return counts.ConsecutiveFailures > 5
    },
})

result, err := cb.Execute(func() (interface{}, error) {
    return callService()
})

// 3. Retry with backoff
import "github.com/cenkalti/backoff"

operation := func() error {
    _, err := callService()
    return err
}

expBackoff := backoff.NewExponentialBackOff()
expBackoff.MaxElapsedTime = 1 * time.Minute

err := backoff.Retry(operation, expBackoff)

// 4. API Gateway pattern
type Gateway struct {
    userSvc    string
    orderSvc   string
    productSvc string
}

func (g *Gateway) route(req *http.Request) string {
    switch {
    case strings.HasPrefix(req.URL.Path, "/users"):
        return g.userSvc
    case strings.HasPrefix(req.URL.Path, "/orders"):
        return g.orderSvc
    default:
        return g.productSvc
    }
}
```

**Patterns:** Strangler Fig, Circuit Breaker, Retry, API Gateway, Saga, CQRS.

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