Merge branch 'benchmarks' into 'master'

CONTRIBUTORS

benchmark/README.md

benchmark/bench_plot_test.go

benchmark/bench_test.go

benchmark/benchmarks.go

benchmark/common.go

benchmark/go.mod

benchmark/go.sum

benchmark/out/benchmarkInsert_memory:false.png

benchmark/out/benchmarkInsert_memory:true.png

benchmark/out/benchmarkSelect_memory:false.png

benchmark/out/benchmarkSelect_memory:true.png

benchmark/plot.go

benchmark/util.go

cgo_test.go