code: func (r Network_Tunnel_Module_Context) AddCustomerSubnetToNetworkTunnel(subnetId *int) (resp bool, err error) {
  	params := []interface{}{
  		subnetId,
  	}
  	err = r.Session.DoRequest("SoftLayer_Network_Tunnel_Module_Context", "addCustomerSubnetToNetworkTunnel", params, &r.Options, &resp)
  	return
  }
docs: // Associates a remote subnet to the network tunnel.  When a remote subnet is associated, a network tunnel will allow the customer (remote) network to communicate with the private and service subnets on the SoftLayer network which are on the other end of this network tunnel.
  //
  // NOTE:  A network tunnel's configurations must be applied to the network device in order for the association described above to take effect.