func WithGeo(fn func(net.IP) Geo) Option {
	return func(i *Instance) {
		i.geolookup = fn
	}
}
WithGeo replaces the default geographic lookup function
package fastlike
import (
	"io"
	"net"
	"net/http"
	"os"
)
type Option func(*Instance)
func WithBackend(name string, h http.Handler) Option {
	return func(i *Instance) {
		i.addBackend(name, h)
	}
}
func WithDefaultBackend(fn func(name string) http.Handler) Option {
	return func(i *Instance) {
		i.defaultBackend = fn
	}
}