code: func NewTCP6Server(ctx context.Context, spec string) (StreamServer, error) {
  	return newTCPServerImpl(ctx, "tcp6", spec, net.IPv6loopback)
  }
docs: // NewTCP6Server creates a new TCP/IP6 stream server.
  //
  // spec is a string of the form [addr][:port].
  //
  // If addr is not empty, it will be an IPv6 network address to bind to. If it
  // is empty, the StreamServer will bind exclusively to localhost.
  //
  // port must be a valid, available port. It may be omitted or <=0, in which case
  // an ephemeral port will be chosen by the system. Note that, in this case, the
  // caller cannot prescribe the port in advance, and must discover it via
  // exported stream server parameters (externally) or by calling Address
  // (internally).