code: func (st *stateTracker) DelNick(n string) *Nick {
  	st.mu.Lock()
  	defer st.mu.Unlock()
  	if nk, ok := st.nicks[n]; ok {
  		if nk == st.me {
  			logging.Warn("Tracker.DelNick(): won't delete myself.")
  			return nil
  		}
  		st.delNick(nk)
  		return nk.Nick()
  	}
  	logging.Warn("Tracker.DelNick(): %s not tracked.", n)
  	return nil
  }
docs: // Removes a nick from being tracked.