After making the change in the golang version, I saw it go as low as 867.61ms.

The JVM is very good at inlining. It's not perfect obviously, but in this benchmark just using an `int[]` wrapped in a class (similar to an ArrayList) produced quicker results than golang. I'm not surprised, since the golang compiler doesn't generate the greatest code.

I tried with Valhalla, with the following array wrapper, and I saw it run as quick as 667ms.

    stretch tree of depth 22  check: 8388607
    2097152  trees of depth 4  check: 65011712
    524288  trees of depth 6  check: 66584576
    131072  trees of depth 8  check: 66977792
    32768  trees of depth 10  check: 67076096
    8192  trees of depth 12  check: 67100672
    2048  trees of depth 14  check: 67106816
    512  trees of depth 16  check: 67108352
    128  trees of depth 18  check: 67108736
    32  trees of depth 20  check: 67108832
    long lived tree of depth 21  check: 4194303
    0.667455718

This is the Java Tree and array wrapper code I used

    inline class Tree {
     public int left; 
     public int right;

     public Tree(int left, int right) {
      this.left = left;
      this.right = right;
     }
    }
    
    ///////////////////////////////////////////////////////////////////////////////
    // Copyright (c) 2001, Eric D. Friedman All Rights Reserved.
    //
    // This library is free software; you can redistribute it and/or
    // modify it under the terms of the GNU Lesser General Public
    // License as published by the Free Software Foundation; either
    // version 2.1 of the License, or (at your option) any later version.
    //
    // This library is distributed in the hope that it will be useful,
    // but WITHOUT ANY WARRANTY; without even the implied warranty of
    // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    // GNU General Public License for more details.
    //
    // You should have received a copy of the GNU Lesser General Public
    // License along with this program; if not, write to the Free Software
    // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
    ///////////////////////////////////////////////////////////////////////////////
    
    final class TIntArrayList {
     protected Tree[] _data;
     protected int _pos;
     public TIntArrayList() {
      _data = new Tree[0];
      _pos = 0;
     }
    
     public void ensureCapacity(int capacity) {
      if (capacity > _data.length) {
       int newCap = Math.max(_data.length << 1, capacity);
       Tree[] tmp = new Tree[newCap];
       System.arraycopy(_data, 0, tmp, 0, _data.length);
       _data = tmp;
      }
     }
     public int size() {
      return _pos;
     }
    
     public void add(Tree val) {
      ensureCapacity(_pos + 1);
      _data[_pos++] = val;
     }
    
     public Tree get(int offset) {
      return _data[offset];
     }
    
     public void resetQuick() {
      _pos = 0;
     }
    }