#TIL

The best job at Google

Recently, I came across two things I would call "Easter Eggs" in Google. The first happened while I was researching Cordyceps to add some facts to my review of Last of Us. I noticed that Google lets y…

René Fischer·Dec 31·4 min read

Preventing accidental struct copies in Go

Prevent dangerous struct copies with noCopy sentinel and go vet's copylock checker. Protect mutexes and sync primitives from value copies.

Redowan Delowar·Apr 21·4 min read

Go TIL Concurrency

Go 1.24's "tool" directive

Pin tool versions in Go 1.24 with the new 'tool' directive. Replace tools.go pattern with native go.mod support for project tooling.

Redowan Delowar·Apr 13·4 min read

Go TIL DevOps

Capturing console output in Go tests

Test functions that write to stdout/stderr in Go by capturing output with os.Pipe. Learn patterns to avoid deadlocks in concurrent tests.

Redowan Delowar·Apr 12·4 min read

Go Testing TIL

Why does Go's io.Reader have such a weird signature?

Understand why io.Reader takes a byte slice parameter instead of returning one. Learn about heap allocations and buffer reuse in Go streams.

Redowan Delowar·Feb 8·3 min read

Go TIL Performance

Dynamic shell variables

Learn variable indirection in Bash with ${!var} syntax. Build context-aware configs, function dispatch, and dynamic variable name resolution.

Redowan Delowar·Jan 11·3 min read

Shell Unix TIL CLI

Injecting Pytest fixtures without cluttering test signatures

Clean up pytest test signatures using @pytest.mark.usefixtures to inject implicit fixtures without autouse or unused parameter warnings.

Redowan Delowar·Dec 2·2 min read

Python TIL Pytest Testing

Explicit method overriding with @typing.override

Catch method override errors at type-check time with Python's @override decorator from PEP 698, preventing typos and signature mismatches.

Redowan Delowar·Nov 6·2 min read

Python TIL Typing

Quicker startup with module-level getattr

Speed up Python module imports with __getattr__ from PEP 562 for lazy loading, deprecation warnings, and dynamic attribute access.

Redowan Delowar·Nov 3·3 min read

Python TIL Performance

Docker mount revisited

Master Docker mount types: volumes, bind mounts, tmpfs, and build cache. Clear syntax comparison between -v and --mount options with docker-compose.

Redowan Delowar·Oct 22·5 min read

TIL Docker DevOps

Discovering direnv

Automate environment variables per directory with direnv. Load .envrc files on entry, unload on exit. Integrate with Python venv and uv workflow.

Redowan Delowar·Oct 2·6 min read

TIL Shell Unix CLI

Bash namerefs for dynamic variable referencing

Master Bash namerefs with declare -n to create dynamic variable references. Build generic functions for arrays and associative arrays without eval.

Redowan Delowar·Sep 20·5 min read

Shell Unix TIL CLI

Shades of testing HTTP requests in Python

Test HTTP requests in Python with pytest-httpx for full mocking, respx for pattern matching, or VCR.py for recording real responses.

Redowan Delowar·Sep 2·3 min read

Python API Testing TIL

Taming parametrize with pytest.param

Write readable parametrized tests with pytest.param for better test names, conditional skips, custom IDs, and structured test data.

Redowan Delowar·Aug 28·2 min read

Python Testing TIL Pytest

HTTP requests via /dev/tcp

Make raw HTTP requests with Bash's /dev/tcp file descriptor. Build health check scripts without curl or wget using TCP socket connections.

Redowan Delowar·Aug 8·2 min read

TIL Shell Unix Networking

The *nix install command

Replace mkdir, cp, and chmod with a single install command. Copy files, create directories, and set permissions in one step with GNU coreutils.

Redowan Delowar·Jul 28·2 min read

Shell Unix TIL CLI

TypeIs does what I thought TypeGuard would do in Python

Understand TypeIs vs TypeGuard in Python: TypeIs provides more intuitive type narrowing by narrowing both positive and negative branches.

Redowan Delowar·Apr 27·4 min read

Python Typing TIL

Strategy pattern in Go

Replace inheritance with the Strategy pattern in Go using interfaces. Achieve composable, testable code without class hierarchies.

Redowan Delowar·Feb 17·5 min read

Go TIL Design Patterns

Retry function in Go

Build retry logic in Go without reflection using generics. Implement exponential backoff and configurable retry strategies with type safety.

Redowan Delowar·Feb 4·3 min read

Go TIL Error Handling

Type assertion vs type switches in Go

Master Go type assertions with i.(T) syntax and type switches. Extract concrete types from interfaces safely with ok idiom examples.

Redowan Delowar·Jan 31·5 min read

Go TIL Data Structures

Patching pydantic settings in pytest

Mock pydantic_settings in pytest tests by patching the settings class to prevent flaky tests from environment variable dependencies.

Redowan Delowar·Jan 27·4 min read

Python TIL Testing Pytest

Omitting dev dependencies in Go binaries

Track dev dependencies like golangci-lint in go.mod with a tools.go file and build tags to exclude them from production binaries.

Redowan Delowar·Jan 21·3 min read

Go TIL DevOps

Annotating args and kwargs in Python

Properly annotate Python *args and **kwargs with heterogeneous types using Unpack, TypedDict, and modern type hints from PEP-692.

Redowan Delowar·Jan 8·3 min read

Python Typing TIL

Statically enforcing frozen data classes in Python

Enforce immutable dataclasses at type-check time with @final decorator to catch mutations before runtime without frozen=True performance cost.

Redowan Delowar·Jan 4·3 min read

Python TIL Typing

Debugging dockerized Python apps in VSCode

Set up VSCode debugger for containerized Python applications using debugpy. Step-by-step guide with Docker Compose and launch configurations.

Redowan Delowar·Dec 22·4 min read

Python TIL Docker

Dotfile stewardship for the indolent

Manage dotfiles across devices with GNU Stow. Symlink configuration files from git repo to home directory with simple, idempotent commands.

Redowan Delowar·Sep 27·4 min read

Shell Unix TIL CLI

Self-hosted Google Fonts in Hugo

Host Google Fonts locally in Hugo without CDN dependency. Download woff2 files, configure CSS, and improve performance while maintaining GDPR compliance.

Redowan Delowar·Sep 14·2 min read

TIL Hugo Web

Dummy load balancer in a single Go script

Build a working round-robin load balancer in Go with goroutines and the standard library. No dependencies needed for this educational prototype.

Redowan Delowar·Aug 30·5 min read

Go TIL Networking

Limit goroutines with buffered channels

Control goroutine concurrency with buffered channels as semaphores. Prevent resource exhaustion with backpressure patterns in Go workers.

Redowan Delowar·Aug 23·4 min read

Go TIL Concurrency

Writing a TOTP client in Go

Build a TOTP-based 2FA client in Go using the standard library. Generate time-based one-time passwords like Google Authenticator.

Redowan Delowar·Aug 20·3 min read

Go TIL Security

Interface guards in Go

Use compile-time interface guards to verify type conformity in Go without runtime overhead. Learn the var _ Interface = (*Type)(nil) pattern.

Redowan Delowar·Aug 18·2 min read

Go TIL API

Go structured logging with slog

Master Go 1.21's log/slog package for structured logging with levels, JSON output, and attribute grouping. No third-party libraries needed.

Redowan Delowar·Aug 10·7 min read

Go TIL Logging

Taming conditionals with bitmasks

Replace complex nested conditionals with Python's enum.Flag and bitmasks for cleaner, more maintainable logic using bitwise operations.

Redowan Delowar·Jul 29·8 min read

Python TIL

Using DNS record to share text data

Share data via DNS TXT records using dig and base64 encoding. Learn limitations, security concerns, and practical use cases for DNS tunneling.

Redowan Delowar·Jul 17·2 min read

Shell Unix TIL Networking

Memory leakage in Python descriptors

Prevent memory leaks in Python descriptors by using weakref to avoid hard references that prevent garbage collection of validated objects.

Redowan Delowar·Jul 16·4 min read

Python TIL Performance

Unix-style pipelining with Python's subprocess module

Build Unix-style command pipelines in Python using subprocess.run with stdout piping for efficient process chaining and output capture.

Redowan Delowar·Jul 14·5 min read

Python TIL Shell Unix

Enabling repeatable lazy iterations in Python

Create reusable generators by implementing __iter__ in a class, allowing multiple lazy iterations without memory overhead or repeated function calls.

Redowan Delowar·Jul 13·3 min read

TIL Python

Associative arrays in Bash

Learn how to use associative arrays in Bash to create key-value pairs, mimic dictionaries, and manage complex data structures in shell scripts.

Redowan Delowar·May 3·4 min read

Shell Unix TIL Data Structures

Process substitution in Bash

Use process substitution <() to treat command output as files in Bash. Compare directories, process data, and avoid temporary files with this technique.

Redowan Delowar·Apr 30·6 min read

Shell Unix TIL

Dynamic menu with select statement in Bash

Build interactive CLI menus with Bash select statement. Create user-friendly command-line tools with option selection and function dispatch.

Redowan Delowar·Apr 29·3 min read

Shell Unix TIL CLI

#TIL

The best job at Google

Preventing accidental struct copies in Go

Go 1.24's "tool" directive

Capturing console output in Go tests

Why does Go's io.Reader have such a weird signature?

Dynamic shell variables

Injecting Pytest fixtures without cluttering test signatures

Explicit method overriding with @typing.override

Quicker startup with module-level __getattr__

Docker mount revisited

Discovering direnv

Bash namerefs for dynamic variable referencing

Shades of testing HTTP requests in Python

Taming parametrize with pytest.param

HTTP requests via /dev/tcp

The *nix install command

TypeIs does what I thought TypeGuard would do in Python

Strategy pattern in Go

Retry function in Go

Type assertion vs type switches in Go

Patching pydantic settings in pytest

Omitting dev dependencies in Go binaries

Annotating args and kwargs in Python

Statically enforcing frozen data classes in Python

Debugging dockerized Python apps in VSCode

Dotfile stewardship for the indolent

Self-hosted Google Fonts in Hugo

Dummy load balancer in a single Go script

Limit goroutines with buffered channels

Writing a TOTP client in Go

Interface guards in Go

Go structured logging with slog

Taming conditionals with bitmasks

Using DNS record to share text data

Memory leakage in Python descriptors

Unix-style pipelining with Python's subprocess module

Enabling repeatable lazy iterations in Python

Associative arrays in Bash

Process substitution in Bash

Dynamic menu with select statement in Bash

Quicker startup with module-level getattr