update sni handler

handler/sni/conn.go

@@ -1,20 +1,10 @@
 package sni
 
 import (
-	"net"
+	"io"
 )
 
-type cacheConn struct {
-	net.Conn
-	buf []byte
-}
-
-func (c *cacheConn) Read(b []byte) (n int, err error) {
-	if len(c.buf) > 0 {
-		n = copy(b, c.buf)
-		c.buf = c.buf[n:]
-		return
-	}
-
-	return c.Conn.Read(b)
+type readWriter struct {
+	io.Reader
+	io.Writer
 }