servername is supported when tls is enabled

[zhyocean]

The genSslConfig function expects to set the servername and version itself

For example

return &tls.Config{
		ServerName:         serverName,
		Certificates:       []tls.Certificate{clientCert},
		RootCAs:            rootCAPool,
		InsecureSkipVerify: *sslInsecureSkipVerify,
                MinVersion:   tls.VersionTLS12,
	        MaxVersion:   tls.VersionTLS12,
	}, nil

The value of the serverName、MinVersion、MaxVersion allows me to pass arguments