Explain type assertion and type switch with real-world examples.
Type assertion extracts the concrete type from an interface value. A type switch checks multiple possible types in sequence, and is commonly used when handling JSON or errors.
Type assertion
Type switch — real-world middleware error handling
Real-world use: encoding/json unmarshals into interface{} where numbers become float64, objects become map[string]interface{}, and arrays become []interface{}. Type switches are essential for processing such dynamic data safely.