code: func (t *Tree) Get(k int64) (v *primitive, ok bool) {
  	q := t.r
  	if q == nil {
  		return
  	}
  
  	for {
  		var i int
  		if i, ok = t.find(q, k); ok {
  			switch x := q.(type) {
  			case *x:
  				q = x.x[i+1].ch
  				continue
  			case *d:
  				return x.d[i].v, true
  			}
  		}
  		switch x := q.(type) {
  		case *x:
  			q = x.x[i].ch
  		default:
  			return
  		}
  	}
  }
docs: // Get returns the value associated with k and true if it exists. Otherwise Get
  // returns (zero-value, false).