Expose TLS connection state whne possible

I would like to be able to report things like ciphers,
tls or not, verified or not etc in nats account info
where its hows other connection properties but had
no way to get at this information

Signed-off-by: R.I.Pienaar <rip@devco.net>

nats.go

@@ -168,6 +168,7 @@ var (
 	ErrStreamNameAlreadyInUse       = errors.New("nats: stream name already in use")
 	ErrMaxConnectionsExceeded       = errors.New("nats: server maximum connections exceeded")
 	ErrBadRequest                   = errors.New("nats: bad request")
+	ErrConnectionNotTLS             = errors.New("nats: connection is not tls")
 )
 
 func init() {
@@ -1807,6 +1808,24 @@ func (nc *Conn) makeTLSConn() error {
 	return nil
 }
 
+// TLSConnectionState retrieves the state of the TLS connection to the server
+func (nc *Conn) TLSConnectionState() (tls.ConnectionState, error) {
+	if !nc.isConnected() {
+		return tls.ConnectionState{}, ErrDisconnected
+	}
+
+	nc.mu.RLock()
+	conn := nc.conn
+	nc.mu.RUnlock()
+
+	tc, ok := conn.(*tls.Conn)
+	if !ok {
+		return tls.ConnectionState{}, ErrConnectionNotTLS
+	}
+
+	return tc.ConnectionState(), nil
+}
+
 // waitForExits will wait for all socket watcher Go routines to
 // be shutdown before proceeding.
 func (nc *Conn) waitForExits() {

test/basic_test.go

@@ -110,6 +110,19 @@ func TestLeakingGoRoutinesOnFailedConnect(t *testing.T) {
 	checkNoGoroutineLeak(t, base, "failed connect")
 }
 
+func TestTLSConnectionStateNonTLS(t *testing.T) {
+	s := RunDefaultServer()
+	defer s.Shutdown()
+
+	nc := NewDefaultConnection(t)
+	defer nc.Close()
+
+	_, err := nc.TLSConnectionState()
+	if err != nats.ErrConnectionNotTLS {
+		t.Fatalf("Expected a not tls error, got: %v", err)
+	}
+}
+
 func TestConnectedServer(t *testing.T) {
 	s := RunDefaultServer()
 	defer s.Shutdown()

test/conn_test.go

@@ -161,6 +161,14 @@ func TestServerSecureConnections(t *testing.T) {
 	}
 	nc.Flush()
 
+	state, err := nc.TLSConnectionState()
+	if err != nil {
+		t.Fatalf("Expected connection state: %v", err)
+	}
+	if !state.HandshakeComplete {
+		t.Fatalf("Expected valid connection state")
+	}
+
 	if err := Wait(checkRecv); err != nil {
 		t.Fatal("Failed receiving message")
 	}