test.go

package main

import (
	"context"
	"errors"
	"log"
	"time")

var totalInventory int

func AddToInventory(_ context.Context,inventory int) {
	if err:=process(inventory);err!=nil{
		log.Print("Inventory is not valid")
	}
}

func process(inventory int) error{
	if inventory<0{
		return errors.New("inventory could not be negative")
	}

	// It takes two seconds to process the request.
	time.Sleep(time.Second * 2)

	log.Print("inventory proceed successfully")
	totalInventory += inventory
	return nil
}

func main() {
	ctx:=context.Background()
	addInventories(ctx)
}

func addInventories(ctx context.Context){
	for i:=0;i<10;i++{
		AddToInventory(ctx,i)
	}
}