Pass client configuration as an argument

The ClientCommonConf, configuration file path, and server UDP port are
now passed around as arguments instead of being shared between
components as global variables. This allows for multiple clients to
exist in the same process, and allows client.Session to be used as a
library more easily.

client/visitor.go

@@ -23,7 +23,6 @@ import (
 	"sync"
 	"time"
 
-	"github.com/fatedier/frp/g"
 	"github.com/fatedier/frp/models/config"
 	"github.com/fatedier/frp/models/msg"
 	"github.com/fatedier/frp/utils/log"
@@ -193,13 +192,13 @@ func (sv *XtcpVisitor) handleConn(userConn frpNet.Conn) {
 	defer userConn.Close()
 
 	sv.Debug("get a new xtcp user connection")
-	if g.GlbClientCfg.ServerUdpPort == 0 {
+	if sv.ctl.serverUDPPort == 0 {
 		sv.Error("xtcp is not supported by server")
 		return
 	}
 
 	raddr, err := net.ResolveUDPAddr("udp",
-		fmt.Sprintf("%s:%d", g.GlbClientCfg.ServerAddr, g.GlbClientCfg.ServerUdpPort))
+		fmt.Sprintf("%s:%d", sv.ctl.clientCfg.ServerAddr, sv.ctl.serverUDPPort))
 	if err != nil {
 		sv.Error("resolve server UDP addr error")
 		return