How to set TLSv1.2 when using openconnect client

[Shen Alex]

When I install openconnect client on cento6.5 and try to connect to
ocserv(disable sslv3). It shows:

attempting to connect to server x.x.x.x:443
SSL negotiation with xxxxxxxxxxxxxxxxxxxxxx
SSL connection failure
139933011761000:error:1408F10B:SSL routines:SSL3_GET_RECORD:wrong
version number:s3_pkt.c:339:
Failed to open HTTPS connection to xxxxxxxxxxxxxxxxxx
GET https://xxxxxxxxxxxxxxxxx/
Attempting to connect to server x.x.x.x:443
SSL negotiation with xxxxxxxxxxxxxxxxxxxxxxx
SSL connection failure
139933011761000:error:1408F10B:SSL routines:SSL3_GET_RECORD:wrong
version number:s3_pkt.c:339:
Failed to open HTTPS connection to xxxxxxxxxxxxxxxx
Failed to obtain WebVPN cookie

I want to set ssl version manually.(like "curl -1","openssl -tls1",etc.)
But I couldn't find any settings about it in "man openconnect".

Pls tell me how to fix it. Thanks