Switch vs map performance in Go

results.txt

$ go test -bench=.
goos: darwin
goarch: amd64
pkg: github.com/localhots/playground/switch_vs_map
BenchmarkSwitch-8       	2000000000	         0.34 ns/op
BenchmarkSwitchMiss-8   	2000000000	         0.64 ns/op
BenchmarkMap-8          	300000000	         4.11 ns/op
BenchmarkMapMiss-8      	200000000	         8.18 ns/op
PASS
ok  	github.com/localhots/playground/switch_vs_map	6.219s

switchvsmap.go

package switchvsmap

func withSwitch(a int) bool {
	switch a {
	case 1, 2, 3:
		return true
	default:
		return false
	}
}

var m = map[int]struct{}{
	1: struct{}{},
	2: struct{}{},
	3: struct{}{},
}

func withMap(a int) bool {
	_, ok := m[a]
	return ok
}

switchvsmap_test.go

package switchvsmap

import "testing"

func BenchmarkSwitch(b *testing.B) {
	for i := 0; i < b.N; i++ {
		withSwitch(1)
	}
}

func BenchmarkSwitchMiss(b *testing.B) {
	for i := 0; i < b.N; i++ {
		withSwitch(5)
	}
}

func BenchmarkMap(b *testing.B) {
	for i := 0; i < b.N; i++ {
		withMap(1)
	}
}

func BenchmarkMapMiss(b *testing.B) {
	for i := 0; i < b.N; i++ {
		withMap(5)
	}
}