in docker/watcher.go [198:208]
func (w *watcher) Containers() map[string]*Container {
w.RLock()
defer w.RUnlock()
res := make(map[string]*Container)
for k, v := range w.containers {
if !w.shortID || len(k) != shortIDLen {
res[k] = v
}
}
return res
}