func (limiter *Limiter) GetIP(r *http.Request) net.IP {
	return GetIP(r, limiter.Options)
}
GetIP returns IP address from request.
package limiter
import (
	"net"
	"net/http"
	"strings"
)
var (
	DefaultIPv4Mask = net.CIDRMask(32, 32)
	DefaultIPv6Mask = net.CIDRMask(128, 128)
)