Mark McDonnell Integralist

Discoverable Test Config in Go: Use Flags

Summary of rednafi.com/go/test-config-with-flags.

The article compares three ways to toggle tests in Go (snapshot, integration, real-vs-mock) and argues for custom flags.

1. Build tags — discouraged

//go:build snapshot

Go "Shebang": Running Go Files as Scripts

Summary of lorentz.app: go-shebang by Lorentz Kinde (2025-12).

The trick

Prepend this line to a .go file, chmod +x, then run it directly:

//usr/local/go/bin/go run "$0" "$@"; exit

In MySQL, a Virtual Column (specifically known as a Generated Column) is a column whose value is automatically calculated from an expression or other columns in the same table, rather than being explicitly inserted or updated by a user.

Think of it like a formula in an Excel spreadsheet: you define the rule once, and the database ensures the data stays in sync.

The Two Types of Generated Columns

MySQL offers two "flavors" of these columns, and the distinction is mostly about storage space versus CPU performance:

Documentation Principles & Best Practices

The primary goal of documentation is to reduce friction for the reader. While the best starting point is simply ensuring a README.md exists, adhering to the following pillars will significantly improve the quality and longevity of your technical writing.

Prioritize Brevity and Professionalism

Be Concise: Value the reader’s time. Use AI as a tool to trim wordy explanations and get straight to the point.
Maintain an Even Tone: Avoid letting personal frustrations or over-enthusiasm color the technical content. Aim for a "neutral-expert" voice that remains consistent from start to finish.

Eliminate Assumptions

Define Your Terms: Never assume a concept is "common knowledge."
External Context: Use hyperlinks to Wikipedia or official documentation for industry terms, protocols, or third-party tools to ensure readers of all levels can follow along.

🚀 MySQL EXPLAIN: The Ultimate Performance Guide

Database optimization can feel like a dark art, but the EXPLAIN command is your "Matrix vision." It reveals how MySQL plans to execute your query before you run it.

1. The Starting Line: Slow Query Log

You can't fix what you can't find. Use the Slow Query Log to catch queries that exceed a specific time threshold.

Prometheus Metric Types: A Quick Reference

This guide explains the four core Prometheus metric types, including common "patterns" that might seem counter-intuitive at first glance.

1. Counter

Definition: A cumulative metric that represents a single monotonically increasing counter. Its value can only increase or be reset to zero on restart.

Best for: "How many times has X happened?"
Examples: Total HTTP requests, total errors, bytes received.

https://www.w3schools.com/tags/ref_urlencode.ASP

" %22
, %2C
: %3A
= %3D
\ %5C
[ %5B
] %5D

In a multi-language repository—for example, one that includes both Go and Ruby—you can run into conflicts around the vendor/ directory. Ruby commonly uses a vendor/ directory to store dependencies, but Go’s toolchain assumes that a vendor/ directory follows its own vendoring format (including the modules.txt file that defines vendored modules).

If Ruby’s vendor/ directory is present, the Go toolchain may attempt to interpret it as a Go vendoring directory, leading to unexpected errors.

To prevent this, configure Go to use module mode explicitly and ignore the vendor/ directory (which, in this case, is only relevant to Ruby):

Add -mod=mod to commands such as go build and go test.
Set a global flag with export GOFLAGS=-mod=mod for commands like go tool that do not expose a -mod flag directly.

	// This code demonstrates how you can embed a type,
	// and have it satisfy an interface (`ProblemDetailer`)
	// but only for the embedded type.
	// This works because the interface uses an unexported method,
	// that is part of the embedded type's package.
	// https://go.dev/play/p/7lbikIyPHi1
	//
	// IMPORTANT: If the `isProblem` inteface method was exported (i.e `IsProblem`),
	// then our `Fake` struct would pass the `.(errorsx.ProblemDetailer)` type assertion
	// e.g. https://go.dev/play/p/pPD3OgtiyHx

	// First complete match wins.
	// Because exact children are tried before `` which is tried before `*`.
	// The most-specific rule wins without an explicit priority sort.
	package redirect

	import (
	"fmt"
	"strings"
	)