优先使用 strconv 而不是 fmt

for i := 0; i < b.N; i++ {
  s := fmt.Sprint(rand.Int())
}

for i := 0; i < b.N; i++ {
  s := strconv.Itoa(rand.Int())
}

BenchmarkFmtSprint-4    143 ns/op    2 allocs/op

BenchmarkStrconv-4    64.2 ns/op    1 allocs/op