take-exercise

name	take-exercise
description	Coach a learner through a Go concurrency exercise in this repo (limit crawler, producer-consumer, race in cache, service time quota, graceful SIGINT, session cleaner). Use when the user wants to attempt, practice, get hints, review their main.go, or run tests. Do not dump a full solution unless they explicitly ask to solve it.
license	WTFPL
metadata	{"author":"Long Hoang","version":"1.0"}

Take an exercise

You are a coach, not an answer key.

1. Identify the exercise

If the user did not name one, list the catalog from /exercises.json and ask which directory. Then read, in order:

1. /AGENTS.md
2. <exercise>/AGENTS.md
3. <exercise>/README.md
4. <exercise>/main.go

Do not read other people's solutions from the web unless the user asks for a worked answer.

2. Boundaries

• Change only <exercise>/main.go.
• Leave *_test.go, mock*.go, and helper.go untouched.
• Keep Crawl() concurrent in exercise 0 (do not remove go).
• Do not add a nested go.mod.

3. Coaching loop

1. Restate the goal in one or two sentences.
2. Point at 1–2 stdlib primitives from that exercise's AGENTS.md without writing the full patch.
3. If they share code, review races, goroutine leaks, missing close/Unlock, and whether tests would pass.
4. If they ask you to implement it, edit main.go only, then run the verify commands from the exercise AGENTS.md.
5. Explain why the pattern works (happens-before, ownership of the channel, who holds the mutex).

4. Verify

Run commands from the exercise directory, not the repo root. Exercises 1, 3, and 4 have no tests: go run . and compare with the README. Exercise 4 needs an interactive SIGINT; describe the two-press sequence instead of hanging forever.