How to Build an Extensible Application with Go

Build extensible Go applications by defining interfaces for core behaviors and implementing them with concrete types, allowing you to swap implementations without changing client code. This approach, demonstrated in the net/rpc package's transition from gob to JSON, relies on defining a ServerCodec interface that abstracts the wire format, enabling new formats like jsonServerCodec to be added simply by implementing the interface methods.

type ServerCodec interface {
	ReadRequestHeader(*Request) error
	ReadRequestBody(interface{}) error
	WriteResponse(*Response, interface{}) error
	Close() error
}

func sendResponse(sending *sync.Mutex, req *Request, reply interface{}, enc ServerCodec, errmsg string) {
	// Logic uses enc interface, agnostic of gob or json implementation
}

Extensibility in Go means designing your code so you can add new features without breaking existing ones. Instead of hard-coding specific behaviors, you define a contract (an interface) that different parts of your program can follow. Think of it like a USB port: you can plug in a mouse, a keyboard, or a drive, and the computer works with all of them because they all follow the same connection rules.