Go benchmark StringBuilder with Fprintf

bench_test.go

package main

import (
	"fmt"
	"strconv"
	"strings"
	"testing"
)

func dummy(s string) {}

func BenchmarkStringBuilder(b *testing.B) {
	for i := 0; i < b.N; i++ {
		var b strings.Builder
		b.WriteString("a=")
		fmt.Fprintf(&b, "%d", 12345)
		dummy(b.String())
	}
}

func BenchmarkByteSlice(b *testing.B) {
	for i := 0; i < b.N; i++ {
		var b []byte
		b = append(b, "a="...)
		b = strconv.AppendInt(b, 12345, 10)
		dummy(string(b))
	}
}

func BenchmarkStringList(b *testing.B) {
	for i := 0; i < b.N; i++ {
		var b []string
		b = append(b, "a=")
		b = append(b, fmt.Sprintf("%d", 12345))
		dummy(strings.Join(b, ""))
	}
}

$ go test -bench . -benchmem | tee bench.txt
goos: linux
goarch: amd64
BenchmarkStringBuilder-2         7166857               164 ns/op              40 B/op          2 allocs/op
BenchmarkByteSlice-2            24701048                48.5 ns/op             8 B/op          1 allocs/op
BenchmarkStringList-2            4430044               271 ns/op              64 B/op          4 allocs/op
PASS

$ go version
go version go1.13.1 linux/amd64