func (c *connectedUDPConn) WriteTo(b []byte, addr net.Addr) (int, error) {
	writer, ok := c.PacketConn.(io.Writer)
	if ok {
		return writer.Write(b)
	}
	return c.PacketConn.WriteTo(b, addr)
}
WriteTo redirects all writes to the Write syscall, which is 4 times faster.
package kcp
import (
	"io"
	"net"
	"net/url"
	kcp "github.com/xtaci/kcp-go"
	"github.com/yinqiwen/gsnova/common/channel"
	"github.com/yinqiwen/gsnova/common/dns"
	"github.com/yinqiwen/gsnova/common/logger"
	"github.com/yinqiwen/gsnova/common/mux"
	"github.com/yinqiwen/gsnova/common/netx"
	"github.com/yinqiwen/pmux"
)
type connectedUDPConn struct{ net.PacketConn }