Original file: https://github.com/miry/samples/blob/master/benchmarks/hash_test.go. Used for Medium article.

access_test.go

package benchmarks

import (
	"fmt"
	"math/rand"
	"testing"
)

/*
BenchmarkAccessStructure show compare metrics between data strucuture and number of items.
*/
func BenchmarkAccessStructure(b *testing.B) {
	for _, size := range []int{1, 10, 100, 1000, 10000, 100000, 1000000} {
		benchmarkAccessStructure(b, size)
	}
}

func benchmarkAccessStructure(b *testing.B, size int) {
	var indexes = make([]int, size, size)
	var arr = make([]int, size, size)
	var hash = make(map[int]int)

	rand.Seed(size % 42)
	for i := 0; i < size; i++ {
		indexes[i] = rand.Intn(size)
		arr[i] = i
		hash[i] = i
	}

	b.ResetTimer()

	b.Run(fmt.Sprintf("Array_%d", size), func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			indx := indexes[i%size] % size
			_ = arr[indx]
		}
	})

	b.Run(fmt.Sprintf("Hash_%d", size), func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			indx := indexes[i%size] % size
			_ = hash[indx]
		}
	})
}

benchmark.out

$ go test -bench=.
goos: darwin
goarch: amd64
pkg: github.com/miry/samples/benchmarks
BenchmarkAccessStructure/Array_1-4         	100000000	        25.2 ns/op
BenchmarkAccessStructure/Hash_1-4          	50000000	        35.5 ns/op
BenchmarkAccessStructure/Array_10-4        	50000000	        25.5 ns/op
BenchmarkAccessStructure/Hash_10-4         	30000000	        42.8 ns/op
BenchmarkAccessStructure/Array_100-4       	100000000	        25.2 ns/op
BenchmarkAccessStructure/Hash_100-4        	30000000	        43.6 ns/op
BenchmarkAccessStructure/Array_1000-4      	50000000	        25.5 ns/op
BenchmarkAccessStructure/Hash_1000-4       	20000000	        63.6 ns/op
BenchmarkAccessStructure/Array_10000-4     	100000000	        25.3 ns/op
BenchmarkAccessStructure/Hash_10000-4      	20000000	        73.1 ns/op
BenchmarkAccessStructure/Array_100000-4    	50000000	        25.4 ns/op
BenchmarkAccessStructure/Hash_100000-4     	20000000	        95.6 ns/op
BenchmarkAccessStructure/Array_1000000-4   	50000000	        25.3 ns/op
BenchmarkAccessStructure/Hash_1000000-4    	10000000	       169 ns/op
PASS
ok  	github.com/miry/samples/benchmarks	24.523s