Improvement of binary-trees implementation in Go

CONTRIBUTE SOURCE CODE

Provide a helpful Title

Small improvement over currently fastest binary-trees implementation in Go #4.

Attach your source code file

(Attach a file with complete, tested, source-code. Your implementation of one benchmarks-game-task for publication with our revised BSD license).

Provide an example build command-line

go build main.go

./main 10
stretch tree of depth 11	 check: 4095
1024	 trees of depth 4	 check: 31744
256	 trees of depth 6	 check: 32512
64	 trees of depth 8	 check: 32704
16	 trees of depth 10	 check: 32752
long lived tree of depth 10	 check: 2047

main.go