SammyOina/README.MD

## README.MD

      
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              README.MD
            
          
    Using empty structs as context keys

It is common to use integer types as keys in maps due low memeory allocation leading to better performance.
For example int8 occupies a single byte of memory. An empty struct in golang have a minimum size of zero bytes,
but they may have a size greater than zero due to padding.
The size of an empty struct in Go is implementation-dependent, and it is usually 1 byte or larger to ensure
that each instance of a struct has a unique memory address.
package main

import (
	"fmt"
	"unsafe"
)

type EmptyStruct struct{}

func main() {
	size := unsafe.Sizeof(EmptyStruct{})
	fmt.Println(size) // Output: 0
}

We can therfore assume in terms of performance and memory use,
using empty structs as keys for context values in Go can be a more efficient choice compared to using int8 values.
We can confirm this using a benchmark test.
package main

import (
	"context"
	"testing"
)

func insertGetCtx(key, value interface{}) {
	ctx := context.WithValue(context.Background(), key, value)
	_ = ctx.Value(key)
}

func BenchmarkInsertGetCtx(b *testing.B) {
	val := "some-value"

	b.Run("string-key", func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			type ctxKey string
			const myKey ctxKey = "string-key"
			insertGetCtx(myKey, val)
		}
	})
	b.Run("int-key", func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			type ctxKey int
			const myKey ctxKey = 1
			insertGetCtx(myKey, val)
		}
	})
	b.Run("empty-struct-key", func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			type ctxKey struct{}
			insertGetCtx(ctxKey{}, val)
		}
	})

}

The results of the benchmark form 10,000,000 iterations show our earlier aassumption.
go test -bench=. -benchtime=10000000x                                                                                   ✔ 
goos: linux
goarch: amd64
pkg: test
cpu: Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz
BenchmarkInsertGetCtx/string-key-8         	10000000	        90.75 ns/op
BenchmarkInsertGetCtx/int-key-8            	10000000	        83.70 ns/op
BenchmarkInsertGetCtx/empty-struct-key-8   	10000000	        79.37 ns/op
PASS
ok  	test	2.543s