GoLang bytes slice as a key map. Just convert the slice to string and Go will optimize it https://stackoverflow.com/questions/20297503/slice-as-a-key-in-map https://github.com/golang/go/wiki/CompilerOptimizations#string-and-byte

hostmap.go

package bytesmap

var m = make(map[string]*string)

// this works faster
func GetOrDefaultInline(host []byte) *string {
	hc, found := m[string(host)]
	if !found {
		m[string(host)] = nil
	}
	return hc
}

func GetOrDefault(host []byte) *string {
	hostStr := string(host) // convert bytes to str only once
	hc, found := m[hostStr]
	if !found {
		m[hostStr] = nil
	}
	return hc
}

hostmap_test.go

package bytesmap

import (
	"testing"
)

var host1 = []byte("host1")
var host2 = []byte("host2")
var host3 = []byte("host3")

func TestGetOrDefault(t *testing.T) {
// FAILED: expected 0 allocations, got 6.000000
	n := testing.AllocsPerRun(100, func() {
		GetOrDefault(host1)
		GetOrDefault(host1)
		GetOrDefault(host2)
		GetOrDefault(host2)
		GetOrDefault(host3)
		GetOrDefault(host3)
	})
	if n != 0 {
		t.Fatalf("expected 0 allocations, got %f", n)
	}
}

// Zero allocations i.e. no any garbage
func TestGetOrDefaultInline(t *testing.T) {
	n := testing.AllocsPerRun(100, func() {
		GetOrDefaultInline(host1)
		GetOrDefaultInline(host1)
		GetOrDefaultInline(host2)
		GetOrDefaultInline(host2)
		GetOrDefaultInline(host3)
		GetOrDefaultInline(host3)
	})
	if n != 0 {
		t.Fatalf("expected 0 allocations, got %f", n)
	}
}

Found the optimization golang/go#3512