code: func (sl *SkipList) init(ifc interface{}) {
  	switch ifc.(type) {
  	case uint8:
  		sl.maxLevel = 8
  	case uint16:
  		sl.maxLevel = 16
  	case uint32:
  		sl.maxLevel = 32
  	case uint64, uint:
  		sl.maxLevel = 64
  	}
  	sl.cache = make(nodes, sl.maxLevel)
  	sl.posCache = make(widths, sl.maxLevel)
  	sl.head = newNode(nil, sl.maxLevel)
  }
docs: // init will initialize this skiplist.  The parameter is expected
  // to be of some uint type which will set this skiplist's maximum
  // level.