# 11. Validation Library Selection

* Status: Accepted
* Deciders: Gabriel Radureau, AI Agent
* Date: 2026-04-05
* Implementation Date: 2026-04-05

## Context and Problem Statement

The dance-lessons-coach application needs input validation for API request bodies and configuration values. We need a library that integrates well with Go structs and provides clear error messages.

## Decision Drivers

* Struct-tag-based validation to avoid boilerplate
* Good error messages with field-level detail
* Active maintenance and wide adoption
* Compatibility with existing interface-based design

## Considered Options

* `github.com/go-playground/validator/v10` — struct-tag driven, widely adopted
* `github.com/asaskevich/govalidator` — tag-based but less expressive
* Manual validation — full control, no dependency, high boilerplate

## Decision Outcome

Chosen option: **`go-playground/validator/v10`** because it is the de-facto standard in the Go ecosystem, supports struct-tag annotations, provides field-level error detail, and integrates cleanly with our interface-based design.

## Implementation

`github.com/go-playground/validator/v10 v10.30.2` is present in `go.mod`.
The `pkg/validation/` package wraps the validator for reuse across handlers.

## Links

* [go-playground/validator GitHub](https://github.com/go-playground/validator)