Update nlopes/slack vendor

vendor/golang.org/x/net/websocket/dial.go

@@ -1,24 +0,0 @@
-// Copyright 2015 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package websocket
-
-import (
-	"crypto/tls"
-	"net"
-)
-
-func dialWithDialer(dialer *net.Dialer, config *Config) (conn net.Conn, err error) {
-	switch config.Location.Scheme {
-	case "ws":
-		conn, err = dialer.Dial("tcp", parseAuthority(config.Location))
-
-	case "wss":
-		conn, err = tls.DialWithDialer(dialer, "tcp", parseAuthority(config.Location), config.TlsConfig)
-
-	default:
-		err = ErrBadScheme
-	}
-	return
-}