# Teaching Notes

- Learner's stated mission: implement and maintain a Go backend with MQTT 5 and Mosquitto for vending-device telemetry, logs, status, commands, and updates.
- Learner initially reported studying through Section 5, then reported finishing through Lesson 5A and requested learner-facing lessons through the end of the Section 18 course plan. HTML guides now cover Lessons 9–18; Lesson 11B is optional. Lesson 6–8 HTML guides already existed.
- Learner is a mid-level Go backend engineer with four years of experience and is confident in Go syntax and core language concepts. Do not teach Go basics or recheck Go proficiency; focus Go explanations on design choices and language behavior that materially affects ownership, concurrency, cancellation, error handling, or API shape.
- Learner has junior-level DevOps experience. Advanced delivery and operations lifecycle practices belong in the separate Section 17A lesson, introduced after the operations/diagnostics section and before backend handover; keep the main MQTT implementation path focused on the requested engineering outcomes.
- For code teaching, begin with what the file does, then give each function a short summary followed by detail. Use emojis as visual landmarks.
- Every standalone lesson must contain the complete code needed for that lesson: full contents for files it creates or changes, including imports, types, and integration/wiring. Do not substitute fragments or links to another lesson for omitted code. Clearly distinguish existing prerequisites from new lesson code, and keep code self-contained and consistent with the course checkout.
- Preserve substantive implementation exercises: ask the learner to make and defend design choices, implement the relevant slice, and explain what evidence proves and does not prove. Avoid beginner Go instruction and generic conceptual summaries.
- Keep the Course 7–9 command and session lessons consistent with COURSE.md: in-memory command state is not durable; the Section 8 API is a lab-only unauthenticated endpoint until Section 11; durable command acceptance/recovery begins in Sections 13–14; distinguish retained latest state from queued one-shot delivery and protocol QoS from business effects.
- Keep lessons short and interactive. Do not mark a concept mastered merely because it appeared in a lesson; wait for the learner's answer or implementation. The request to create lessons is not evidence that Lessons 6–18 have been completed.
- Keep examples in the disposable lab and do not modify production systems.