go test -bench BenchmarkCountLetters -benchtime=10000000x -benchmem
goos: windows
goarch: amd64
pkg: benching
cpu: Intel(R) Core(TM) i5-10210U CPU @ 1.60GHz
BenchmarkCountLetters/Test_1-8 10000000 174.0 ns/op 0 B/op 0 allocs/op
BenchmarkCountLetters/Test_2-8 10000000 310.7 ns/op 0 B/op 0 allocs/op
BenchmarkCountLetters/Test_3-8 10000000 619.9 ns/op 136 B/op 2 allocs/op
BenchmarkCountLetters/Test_4-8 10000000 756.2 ns/op 168 B/op 3 allocs/op
BenchmarkCountLetters/Test_5-8 10000000 400.2 ns/op 48 B/op 1 allocs/op
BenchmarkCountLetters/Test_6-8 10000000 1653 ns/op 459 B/op 3 allocs/op
BenchmarkCountLetters/Test_7-8 10000000 37.31 ns/op 0 B/op 0 allocs/op
BenchmarkCountLetters/Test_8-8 10000000 55.49 ns/op 0 B/op 0 allocs/op