bash.log

$ ./test small                                                                                                                                   345ms ? Wed Dec 11 19:35:24 2019
2019/12/11 19:35:25 File Size: 66b
2019/12/11 19:35:26 [before Unmarshal] Alloc = 0 MiB | TotalAlloc = 0 MiB | Sys = 66 MiB | NumGC = 0
2019/12/11 19:35:26 [after Unmarshal] Alloc = 0 MiB | TotalAlloc = 0 MiB | Sys = 66 MiB | NumGC = 0
2019/12/11 19:35:26 [before Marshal] Alloc = 0 MiB | TotalAlloc = 0 MiB | Sys = 66 MiB | NumGC = 0
2019/12/11 19:35:26 [after Marshal] Alloc = 0 MiB | TotalAlloc = 0 MiB | Sys = 66 MiB | NumGC = 0
$ ./test medium                                                                                                                                                                                                       ~/g/s/g/a/awesomeProject ? ./test medium                                                                                                                                          Wed Dec 11 19:35:26 2019
2019/12/11 19:35:29 File Size: 100054b
2019/12/11 19:35:29 [before Unmarshal] Alloc = 0 MiB | TotalAlloc = 0 MiB | Sys = 66 MiB | NumGC = 0
2019/12/11 19:35:29 [after Unmarshal] Alloc = 0 MiB | TotalAlloc = 0 MiB | Sys = 66 MiB | NumGC = 0
2019/12/11 19:35:29 [before Marshal] Alloc = 0 MiB | TotalAlloc = 0 MiB | Sys = 66 MiB | NumGC = 0
2019/12/11 19:35:29 [after Marshal] Alloc = 0 MiB | TotalAlloc = 0 MiB | Sys = 66 MiB | NumGC = 0
$ ./test large                                                                                                                                                                                                      ~/g/s/g/a/awesomeProject ? ./test medium2                                                                                                                                         Wed Dec 11 19:35:29 2019
2019/12/11 19:35:33 File Size: 11500054b
2019/12/11 19:35:33 [before Unmarshal] Alloc = 11 MiB | TotalAlloc = 11 MiB | Sys = 68 MiB | NumGC = 1
2019/12/11 19:35:33 [after Unmarshal] Alloc = 22 MiB | TotalAlloc = 22 MiB | Sys = 68 MiB | NumGC = 2
2019/12/11 19:35:33 [before Marshal] Alloc = 22 MiB | TotalAlloc = 22 MiB | Sys = 68 MiB | NumGC = 2
2019/12/11 19:35:33 [after Marshal] Alloc = 22 MiB | TotalAlloc = 43 MiB | Sys = 68 MiB | NumGC = 3
                                                                                    

main.go

package main

import (
	"encoding/json"
	"fmt"
	"github.com/assada/awesomeProject/data"
	"io/ioutil"
	"log"
	"os"
	"runtime"
)
func check(e error) {
	if e != nil {
		panic(e)
	}
}

func printMemUsage(phase string) {
	var m runtime.MemStats
	runtime.ReadMemStats(&m)

	log.Printf(
		"[%v] Alloc = %v MiB | TotalAlloc = %v MiB | Sys = %v MiB | NumGC = %v",
		phase,
		bToMb(m.Alloc),
		bToMb(m.TotalAlloc),
		bToMb(m.Sys),
		m.NumGC,
	)
}

func bToMb(b uint64) uint64 {
	return b / 1024 / 1024
}

func main() {
	arg := os.Args[1]
	dat, err := ioutil.ReadFile("data/"+arg+".json")
	check(err)

	log.Printf("File Size: %vb", len(dat))

	logStr := new(data.Log)
	printMemUsage("before Unmarshal")
	e := json.Unmarshal(dat, &logStr)
	printMemUsage("after Unmarshal")
	check(e)

	printMemUsage("before Unmarshal")
	bytes, e := json.Marshal(logStr)
	printMemUsage("after Unmarshal")
	check(e)

	fmt.Print(len(bytes) / 1024 / 1024)
}

struct.go

package data

type Log struct {
	RequestId   string `json:"request_id"`
	Data        string `json:"data"`
}