You're working on a Go project where you need to integrate with different payment gateways, each with its own API. How would you design your code to handle this integration in a flexible and extensible way?

Leveraging interfaces in Go, you can define a common payment gateway interface with methods like ProcessPayment(amount float64) error. Each payment gateway can then implement this interface with its own API-specific integration logic. This design promotes flexibility and extensibility, as new payment gateways can be seamlessly integrated by implementing the common interface. It also simplifies testing and maintenance by providing a unified abstraction for interacting with diverse payment gateways.