return error on incorrect request type and default created_at value

client.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
@@ -75,6 +76,10 @@ func (c *Castle) Filter(ctx context.Context, req *Request) (RecommendedAction, e
 		Email:    req.User.Email,
 		Username: req.User.Name,
 	}
+	createdAt := req.CreatedAt
+	if req.CreatedAt.IsZero() {
+		createdAt = time.Now()
+	}
 	r := &castleFilterAPIRequest{
 		Type:         req.Event.EventType,
 		Name:         req.Event.Name,
@@ -83,7 +88,7 @@ func (c *Castle) Filter(ctx context.Context, req *Request) (RecommendedAction, e
 		Params:       params,
 		Context:      req.Context,
 		Properties:   req.Properties,
-		CreatedAt:    req.CreatedAt,
+		CreatedAt:    createdAt,
 	}
 	return c.sendCall(ctx, r, FilterEndpoint)
 }
@@ -97,6 +102,10 @@ func (c *Castle) Risk(ctx context.Context, req *Request) (RecommendedAction, err
 	if req.Context == nil {
 		return RecommendedActionNone, errors.New("request.Context cannot be nil")
 	}
+	createdAt := req.CreatedAt
+	if req.CreatedAt.IsZero() {
+		createdAt = time.Now()
+	}
 	r := &castleRiskAPIRequest{
 		Type:         req.Event.EventType,
 		Name:         req.Event.Name,
@@ -105,7 +114,7 @@ func (c *Castle) Risk(ctx context.Context, req *Request) (RecommendedAction, err
 		User:         req.User,
 		Context:      req.Context,
 		Properties:   req.Properties,
-		CreatedAt:    req.CreatedAt,
+		CreatedAt:    createdAt,
 	}
 	return c.sendCall(ctx, r, RiskEndpoint)
 }
@@ -128,6 +137,8 @@ func (c *Castle) sendCall(ctx context.Context, r castleAPIRequest, url string) (
 	switch request := r.(type) {
 	case *castleFilterAPIRequest, *castleRiskAPIRequest:
 		err = json.NewEncoder(b).Encode(request)
+	default:
+		err = fmt.Errorf("incorrect request type passed as argument.")
 	}
 	if err != nil {
 		return RecommendedActionNone, err