Go functional options

options.go

type Server struct {
	addr    string
	timeout int
	retry   int
	speed   int
}

func NewServer(addr string, opts ...func(*Server)) (*Server, error) {
	srv := new(Server)
	srv.addr = addr
	for _, opt := range opts {
		opt(srv)
	}
	return srv, nil
}

func main() {
	//default
	_, _ = NewServer("localhost")
	
	_, _ = NewServer("localhost", WithTimeout(3000), WithRetry(3))

}

func WithTimeout(timeout int) func(*Server) {
	return func(server *Server) {
		server.timeout = timeout
	}
}

func WithRetry(retry int) func(*Server) {
	return func(server *Server) {
		server.retry = retry
	}
}