عين

Typed Nil in Go

Fri, 05 Dec 2025 19:50:43 +0200

Guess the output

Let’s take this method which is simple nil check

func IsErrNil(err error) {
 println(err == nil)
}

Let’s start directly with snippets and guess their output

func main() {
 var err error
 fmt.Println(err)
 fmt.Println(err == nil)
 IsErrNil(err)
}

What do you think the output is?

If you think that it’s

<nil>
true
true

Then right! Easy, cause in Go default value of error is nil

Let’s go to the next snippet, here I am defining my own custom error type that satisfies the error interface in Go

Gemini API Memory Efficient Way to Handle File Upload

Fri, 01 Aug 2025 14:37:45 +0300

Introduction

Hello, in this post we will design a memory efficient way to take a file from client and communicate it back to the genai go SDK.

Method

If we go the documentation of document processing API notice in the example they are getting the file storing it inside a temporary buffer then using client.Files.UploadFromPath to upload the file from local path, genai, at the moment of writing this blog allow maximum is 20 MB Also the attached PDF which is 19.7 MB is the PDF I will be using in this blog.

Be Aware of Pointer References And Cache

Sat, 21 Jun 2025 20:53:36 +0300

Introduction

I faced a bug, that is so simple, that it took me sometime to find it. Let’s start with the problem, and explain what was happening.

Problem Description

Let’s take a look at this code ( I knew it’s not well written, but it’s a good minimal example)

type S struct {
	Field1 int
}

type X struct {
	S *S
}

type Y struct {
	sm map[string]*S
}

func main() {
	key := "k"
	s := &S{Field1: 10}
	x := X{S: s}
	y := Y{sm: map[string]*S{
		key: s,
	}}
	x.S.Field1 = 20
	fmt.Printf("Changing x reflected in y map: %d\n", y.sm[key]) // prints 20

	fmt.Println("Caching x struct...")
	c := &Cache{}
	xJSON, err := json.Marshal(x)
	if err != nil {
		panic(err)
	}
	c.Put(key, xJSON)

	y.sm[key].Field1 = -100
	fmt.Printf("Field in y map: %d\n", y.sm[key].Field1) // prints -100
	fmt.Printf("Field in x (live without saving to cache): %d\n", x.S.Field1) // prints -100

	v, ok := c.Get(key)
	if !ok {
		panic("not found")
	}
	var xFromCache *X
	err = json.Unmarshal(v, &xFromCache)
	if err != nil {
		panic(err)
	}

	fmt.Println("Reading x from cache...")
	fmt.Printf("After reading from cache: %d\n", xFromCache.S.Field1) // prints 20
}

type Entry struct {
	key string
	value []byte
}

type Cache struct {
	mu sync.Mutex
	entries []Entry
}

func (c *Cache) Put(key string, value []byte) {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.entries = append(c.entries, Entry{
		key: key,
		value: value,
	})
}

func (c *Cache) Get(key string) ([]byte, bool) {
	c.mu.Lock()
	defer c.mu.Unlock()
	for _, entry := range c.entries {
		if entry.key == key {
			return entry.value, true
		}
	}
	return []byte{}, false
}

The problem here that after we changed the values we didn’t save the changes to the cache. If we save the Y struct to the cache, the changes will be reflected only for the Y struct itself, but not for the X struct. so when they are stored in the cache, the changes made to the Y struct will not be reflected in the X struct.

Read From Pipe and Terminal in Same Go App

Sat, 12 Apr 2025 20:08:10 +0300

Introduction

Hello, I wanted to create a small app that do fuzzy matching on what ever passed to it in the pipe. The app will take the input from the pipe, then enter terminal mode to interactive fuzzing.

But there is a problem, that took me a while to figure out how to solve it.

The problem

The problem is that once os.Stdin is used in pipe mode, it can’t be switched to terminal mode for interactive use.

Add Prompt Shortcut to Firefox AI Integration

Sun, 16 Mar 2025 01:51:51 +0200

Introduction

Hello, I wanted a way to boost my Japanese studies, I was thinking of a way that gives smart subtitles no only word to word translation, at first I prototyped a small app that load video and subtitles, then it give meaning of words and some grammar, how ever this takes a lot of time to prepare content and subtitles. So I thought of a way to watch anime in browser, and leverage firefox new AI integration to give me the meaning of words in the context and grammar.

My Programming Philosophy and Rules

Fri, 14 Mar 2025 04:21:50 +0200

Introduction

This blog will be some ideas that I reassemble of how I think about programming. These are subjected to change the more I grow. These are pure personal and opinionated, it’s just a public memo that I would like to revisit from time to time and track how the way I think about programming have changed each time I look at this. A worth noting, that I am not a subject expert. So I touch the surface of different topics. I won’t claim that I know the smallest details about all of the things. Just enough knowledge that get the job done.

PostgreSQL Query Optimization Second Edition Summary

Tue, 18 Feb 2025 18:56:59 +0200

Introduction

Hello, this is a summary of the book PostgreSQL Query Optimization Second Edition after reading mysql now that I am professionally working with postgresql I want to learn more about optimizing queries in postgresql.

These types of summaries are not really for audiences but for me to remember what I read and to be able to reference them later. AI tools these days are so good at this but I like to do this type of summaries for my own learning. Actually each chapter in the book have a summary so :)

Restrict Direct Call to a Method Inside Test in Go

Fri, 06 Dec 2024 01:33:05 +0400

Introduction

Hello, I am going to show a cool trick to restrict direct call to a method inside test in Go. This is useful when you want to make sure that a method is only called from production code and not tests.

Problem

I will put this code, our objective is simple we need to make sure that MyStruct doer have done and confirmed the end of their job.

package demo

import "fmt"

type Doer interface {
	Do()
	EndDo()
}

type MyStruct struct {
	D Doer
}

type DoPrint struct{}

func (d DoPrint) Do() {
	fmt.Println("Doing")
}

func (d DoPrint) EndDo() {
	fmt.Println("End Doing")
}

func (s *MyStruct) Run() {
	s.D.Do()
	defer s.D.EndDo()
}

in other word we need to make sure that when Do is called EndDo is also called. to verify this let’s write a unit test.

Run Infinite Loop Without Frying the CPU in C

Mon, 25 Nov 2024 04:59:15 +0400

Introduction

In this article, I will show you how to run an infinite loop without frying the CPU in C. In Go it’s easy to achieve this by using channels and goroutines. I am new to C and I wanted to see how I can achieve the same thing in C. So if you are an experienced C developer, please let me know if there is a better way to do this.

Learning Japanese: The Journey

Wed, 29 May 2024 02:06:01 +0300

Introduction

This is documentation of my progress in learning Japanese, I will post updates on this same post. I tried to learn Japanese before but stoped because LIFE. Also this is an updated journey, I had old content on this post that I deleted, because it was failure attemp, basically I was trying to learn Japanese using a game on steam, the progress was so slow and unproductive.

Date format is dd-MM-yyyy

PostgreSQL - Experimenting Trigger Under Transaction

Sun, 14 Apr 2024 23:34:38 +0300

Introduction and Motivation

Hello, this blog post will be very light, it’s a small experiment I did to solidify my understanding of triggers under a transaction.

I was working on a piece of code that uses some helper functions, and I was getting a behavior that I wasn’t expecting.

My original guess was that all the trigger runs under the transactions would be done immediately and not after the COMMIT.

Building Distributed Game Server In Go

Mon, 18 Dec 2023 19:16:41 +0200

Introduction

In this blog, I will go through designing a distributed game server and the theory behind it.

The game is Hangman with a Kanna theme. The game itself doesn’t make any sense to be distributed, this is just a project I made for fun to sharpen my skills in building a distributed system.

I will not show any code in this article but rather some theory and architecture, if you have questions feel free to contact me or read the source code at dhangkanna to see the implementation details.

Csharp Wait All Tasks to Finish Without Holding Pointers to Tasks

Sat, 14 Oct 2023 08:39:17 +0300

Introduction

Let’s say you have an old code base, that doesn’t hold pointer to Tasks, and you need to wait all of them to be done on caller side, and you have nested calls so it’s hard to refactor, so you can’t do Task.WhenAll(tasks).Wait(), so we need a wait all tasks to finish before executing code without keeping track of which Tasks are executed.

Coding

C# Task.WhenAll

I will start by show casing how it’s done usually with Task.WhenAll, we will start with a code that does not wait tasks and refactor to wait tasks.

Mysql 8 Query Performance Reference

Sun, 03 Sep 2023 00:20:03 +0300

Introduction and Motivation

Hello I decided to make this complete reference because of a problem I faced at work: a painfully slow query that took 25 seconds to run. Through extensive research and learning, I managed to optimize it to just 1 second. But my journey didn’t stop there; I continued exploring database performance tuning, guided by the book “MySQL 8 Query Performance Tuning.”¹ This blog serves as a summary of some chapters and sections from the book. If you find it intriguing, I encourage you to explore the full version, which delves into many more details and insights.

Generate Time Based One Time Password Like 2FA Apps

Tue, 29 Aug 2023 22:28:12 +0300

Introduction

Hello, I will try to explain in this post how I made my own TOTP(Time Based One Time Password) using c#

Many of us use authenticator apps like google authenticator it basically generate a one time password every X seconds. Then we can use this password to verify login or whatever.

Theory

I will explain the theory behind it in very simple words, Here is some math of how we will generate TOTP¹

Sync Same Git Repo Between Different Version Control Systems

Sun, 27 Aug 2023 14:04:38 +0300

Introduction

Hello, years back I decided to migrate to codeberg because of disagreement with github policies

Now I decided to move back to github, so the problem I faced is that my repos are outdated on github and I need to get the updates from codeberg.

Solution 1

The first solution was to delete repo from github then use import feature in github to import repo from codeberg. That works but we loose a lot of stuff when doing so, like stars.

Copy Null Values From Another Object Using Reflection

Sat, 26 Aug 2023 20:33:57 +0300

Let’s say we have the following class

class Client {
 public string? Name { get; set; }
 public int? Age { get; set; }
}

let’s create two instances from this class

Client client1 = new();
Client client2 = new();

let’s assign name for client1 and age for client2

client1.Name = "Omar";
client2.Age = 23;

Now if we look at memory, we can see that client1 have Age as null and client2 have Name as null.

We need to fill null values in client1 from client2 during runtime, sounds easy! right?

client1.Age = client2.Age;

sure that works, but let’s say our object have over 100 properties. Typing them one by one is boring as 🦆

My personal Setup

Fri, 25 Aug 2023 00:15:07 +0300

Introduction

Hello I am going to write about my personal setup for both work, gaming and learning.

I have 2 machines for now, one laptop for work and gaming pc for home usage.

Work setup

For work I use a ThinkPad P14s Gen 2

Specs	Name
CPU	AMD Ryzen™ 7 PRO 5850U Processor (1.90 GHz, up to 4.40 GHz Max Boost, 8 Cores, 16 Threads, 16 MB Cache)
RAM	32 GB DDR4 3200MHz
OS	Instant OS beta 7

Home setup

For home/gaming setup I use a custom build

About

Mon, 01 Jan 0001 00:00:00 +0000

Hello, I'm Omar ElKhatib, also known online as عين (pronounced Ayn).

You will find me blogging from time to time about things that I found interesting. I love distributed systems, performance, some low level details and architecture.

Professionally I worked as .net and currently a Go developer, tried to learn Rust but never build things with it, currently I am exploring C.

In my freetime I like to watch anime or learn new stuff, I am also a casual gamer, mostly card games.

Contact

Mon, 01 Jan 0001 00:00:00 +0000

khatibomar

OmarElKhatib