Add support for HTTP and SOCKS5 proxies (#127)

As mentioned in https://github.com/davegallant/vpngate/issues/126, adding support for proxies will help bypass issues when vpngate.net is not accessible directly.

This works by:

```sh
# http proxy
sudo vpngate connect --proxy "http://localhost:8080"

# socks5 proxy
sudo vpngate connect --socks5 "127.0.0.1:1080"
```

cmd/connect.go

@@ -16,24 +16,28 @@ import (
 )
 
 var (
-	flagRandom    bool
-	flagReconnect bool
+	flagRandom      bool
+	flagReconnect   bool
+	flagProxy       string
+	flagSocks5Proxy string
 )
 
 func init() {
 	connectCmd.Flags().BoolVarP(&flagRandom, "random", "r", false, "connect to a random server")
 	connectCmd.Flags().BoolVarP(&flagReconnect, "reconnect", "t", false, "continually attempt to connect to the server")
+	connectCmd.Flags().StringVarP(&flagProxy, "proxy", "p", "", "provide a http/https proxy server to make requests through (i.e. 127.0.0.1:8080")
+	connectCmd.Flags().StringVarP(&flagSocks5Proxy, "socks5", "s", "", "provide a socks5 proxy server to make requests through (i.e. 127.0.0.1:1080")
 	rootCmd.AddCommand(connectCmd)
 }
 
 var connectCmd = &cobra.Command{
-	Use:   "connect",
-	
+	Use: "connect",
+
 	Short: "Connect to a vpn server (survey selection appears if hostname is not provided)",
 	Long:  `Connect to a vpn from a list of relay servers`,
 	Args:  cobra.RangeArgs(0, 1),
 	Run: func(cmd *cobra.Command, args []string) {
-		vpnServers, err := vpn.GetList()
+		vpnServers, err := vpn.GetList(flagProxy, flagSocks5Proxy)
 		if err != nil {
 			log.Fatal().Msgf(err.Error())
 			os.Exit(1)

cmd/list.go

@@ -22,7 +22,7 @@ var listCmd = &cobra.Command{
 	Args:  cobra.NoArgs,
 	Run: func(cmd *cobra.Command, args []string) {
 		
-		vpnServers, err := vpn.GetList()
+		vpnServers, err := vpn.GetList(flagProxy, flagSocks5Proxy)
 		if err != nil {
 			log.Fatal().Msgf(err.Error())
 			os.Exit(1)