Five way to build strings (strings builder are coming soon).

strings.go

package main

import (
	"fmt"
	"reflect"
	"testing"
	"unsafe"
)

// goos: darwin
// goarch: amd64
// BenchmarkBuildStringByConcatenating-4   	 2000000	       754 ns/op	     800 B/op	      10 allocs/op
// BenchmarkBuildStringByMasking-4         	20000000	       114 ns/op	       0 B/op	       0 allocs/op
// BenchmarkBuildStringBySprintf-4         	  500000	      2132 ns/op	     960 B/op	      20 allocs/op
// BenchmarkBuildStringByUnsafe-4          	20000000	        76.1 ns/op	       0 B/op	       0 allocs/op

func BenchmarkBuildStringByConcatenating(b *testing.B) {
	base := "https://guard.octolab.net/api/v1/license/"
	ids := []string{
		"072f5a3c-d612-4b91-af13-937e36e2aa93",
		"3303ac29-8982-4220-a405-c5694b3f0baf",
		"43fee265-a980-4bce-bb8b-8e780c67e047",
		"9b8d8fdb-dd04-4632-beff-261b132231a0",
		"8249a5cf-7bfb-4107-9bc0-f1a17dfa90e5",
		"6b3b2eb5-478f-4746-97f8-3a2f2c5b8aef",
		"d8de660b-739b-4bed-a961-df39822bbd3b",
		"1bdb82bc-0077-404d-bf2a-dda69ded1ce4",
		"bff662fd-95a6-4f60-92d9-a052bee6779c",
		"838dc73f-983c-4cac-8690-252a4ea4bbaa",
	}
	var last string
	b.ReportAllocs()
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		for _, id := range ids {
			last = base + id
		}
	}
	if last != "https://guard.octolab.net/api/v1/license/838dc73f-983c-4cac-8690-252a4ea4bbaa" {
		b.Fail()
	}
}

func BenchmarkBuildStringByMasking(b *testing.B) {
	base := []rune("https://guard.octolab.net/api/v1/license/00000000-0000-0000-0000-000000000000")
	ids := [][]rune{
		[]rune("072f5a3c-d612-4b91-af13-937e36e2aa93"),
		[]rune("3303ac29-8982-4220-a405-c5694b3f0baf"),
		[]rune("43fee265-a980-4bce-bb8b-8e780c67e047"),
		[]rune("9b8d8fdb-dd04-4632-beff-261b132231a0"),
		[]rune("8249a5cf-7bfb-4107-9bc0-f1a17dfa90e5"),
		[]rune("6b3b2eb5-478f-4746-97f8-3a2f2c5b8aef"),
		[]rune("d8de660b-739b-4bed-a961-df39822bbd3b"),
		[]rune("1bdb82bc-0077-404d-bf2a-dda69ded1ce4"),
		[]rune("bff662fd-95a6-4f60-92d9-a052bee6779c"),
		[]rune("838dc73f-983c-4cac-8690-252a4ea4bbaa"),
	}
	window := base[len(base)-len(ids[0]):]
	b.ReportAllocs()
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		for _, id := range ids {
			copy(window, id)
		}
	}
	if string(base) != "https://guard.octolab.net/api/v1/license/838dc73f-983c-4cac-8690-252a4ea4bbaa" {
		b.Fail()
	}
}

func BenchmarkBuildStringBySprintf(b *testing.B) {
	base := "https://guard.octolab.net/api/v1/license/%s"
	ids := []string{
		"072f5a3c-d612-4b91-af13-937e36e2aa93",
		"3303ac29-8982-4220-a405-c5694b3f0baf",
		"43fee265-a980-4bce-bb8b-8e780c67e047",
		"9b8d8fdb-dd04-4632-beff-261b132231a0",
		"8249a5cf-7bfb-4107-9bc0-f1a17dfa90e5",
		"6b3b2eb5-478f-4746-97f8-3a2f2c5b8aef",
		"d8de660b-739b-4bed-a961-df39822bbd3b",
		"1bdb82bc-0077-404d-bf2a-dda69ded1ce4",
		"bff662fd-95a6-4f60-92d9-a052bee6779c",
		"838dc73f-983c-4cac-8690-252a4ea4bbaa",
	}
	var last string
	b.ReportAllocs()
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		for _, id := range ids {
			last = fmt.Sprintf(base, id)
		}
	}
	if last != "https://guard.octolab.net/api/v1/license/838dc73f-983c-4cac-8690-252a4ea4bbaa" {
		b.Fail()
	}
}

func BenchmarkBuildStringByUnsafe(b *testing.B) {
	base := "https://guard.octolab.net/api/v1/license/00000000-0000-0000-0000-000000000000"
	hdr := (*reflect.StringHeader)(unsafe.Pointer(&base))
	data := *(*[77]byte)(unsafe.Pointer(hdr.Data))
	hdr.Data = uintptr(unsafe.Pointer(&data))
	ids := [][]byte{
		[]byte("072f5a3c-d612-4b91-af13-937e36e2aa93"),
		[]byte("3303ac29-8982-4220-a405-c5694b3f0baf"),
		[]byte("43fee265-a980-4bce-bb8b-8e780c67e047"),
		[]byte("9b8d8fdb-dd04-4632-beff-261b132231a0"),
		[]byte("8249a5cf-7bfb-4107-9bc0-f1a17dfa90e5"),
		[]byte("6b3b2eb5-478f-4746-97f8-3a2f2c5b8aef"),
		[]byte("d8de660b-739b-4bed-a961-df39822bbd3b"),
		[]byte("1bdb82bc-0077-404d-bf2a-dda69ded1ce4"),
		[]byte("bff662fd-95a6-4f60-92d9-a052bee6779c"),
		[]byte("838dc73f-983c-4cac-8690-252a4ea4bbaa"),
	}
	window := data[len(data)-len(ids[0]):]
	b.ReportAllocs()
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		for _, id := range ids {
			copy(window, id)
		}
	}
	if base != "https://guard.octolab.net/api/v1/license/838dc73f-983c-4cac-8690-252a4ea4bbaa" {
		b.Fail()
	}
}