introspection.go
func (ch *Channel) IntrospectNumConnections() int {
	ch.mutable.RLock()
	numConns := len(ch.mutable.conns)
	ch.mutable.RUnlock()
	return numConns
}
func (ch *Channel) IntrospectNumConnections() int {
	ch.mutable.RLock()
	numConns := len(ch.mutable.conns)
	ch.mutable.RUnlock()
	return numConns
}
// IntrospectNumConnections returns the number of connections returns the number
// of connections. Note: like other introspection APIs, this is not a stable API.