func WithMessageSigning(enabled bool) Option {
	return func(p *PubSub) error {
		if enabled {
			p.signKey = p.host.Peerstore().PrivKey(p.signID)
			if p.signKey == nil {
				return fmt.Errorf("can't sign for peer %s: no private key", p.signID)
			}
		} else {
			p.signKey = nil
			p.signStrict = false
		}
		return nil
	}
}
func WithMessageSigning(enabled bool) Option {
	return func(p *PubSub) error {
		if enabled {
			p.signKey = p.host.Peerstore().PrivKey(p.signID)
			if p.signKey == nil {
				return fmt.Errorf("can't sign for peer %s: no private key", p.signID)
			}
		} else {
			p.signKey = nil
			p.signStrict = false
		}
		return nil
	}
}
// WithMessageSigning enables or disables message signing (enabled by default).