first commit

context_handler/context_handler.go

@@ -0,0 +1,43 @@
+package context_handler
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"time"
+)
+
+type keyType string
+
+const userKey keyType = "userID"
+
+// WithUserID stores user id in context
+func WithUserID(ctx context.Context, userID string) context.Context {
+	return context.WithValue(ctx, userKey, userID)
+}
+
+// FetchRiwayatKursus simulates fetching course history but respects context deadlines/cancel.
+func FetchRiwayatKursus(ctx context.Context) (string, error) {
+	// try to read user ID
+	uid, _ := ctx.Value(userKey).(string)
+	if uid == "" {
+		uid = "unknown"
+	}
+
+	// simulate work that may take up to 2 seconds
+	work := make(chan string, 1)
+
+	go func() {
+		// simulate slower work 1.5s
+		time.Sleep(1500 * time.Millisecond)
+		work <- fmt.Sprintf("history for user %s: [Course-A, Course-B]", uid)
+	}()
+
+	select {
+	case <-ctx.Done():
+		// context timed out or cancelled
+		return "", errors.New("fetch cancelled or timed out: " + ctx.Err().Error())
+	case res := <-work:
+		return res, nil
+	}
+}