Benchmarks test to know how much memory can be saved by using struct{} instead of booleans.

main.go

package main

import (
	"fmt"
	"testing"
)

func benchmarkBooleans(b *testing.B) {
	s := make(map[int]bool)

	for i := 0; i < 1000*b.N; i++ {
		s[2*i] = true
	}
}

func benchmarkStructs(b *testing.B) {
	s := make(map[int]struct{})

	for i := 0; i < 1000*b.N; i++ {
		s[2*i] = struct{}{}
	}
}

func main() {
	boolRes := testing.Benchmark(benchmarkBooleans)
	fmt.Println("booleans:", boolRes.MemString())

	structRes := testing.Benchmark(benchmarkStructs)
	fmt.Println("structs{}:", structRes.MemString())

	fmt.Println("ratio:", float32(boolRes.AllocedBytesPerOp()) / float32(structRes.AllocedBytesPerOp()))
}