Test — Module 13: Web Services and APIs¶

Topic: [[go]] Module: [[go/13. Web Services and APIs]]

Before You Begin¶

[!WARNING] Do not look at ANSWERS.md or your notes during the test. The purpose of this test is to surface what you truly know vs. what you think you know. An inflated score is worthless. An honest score shows you exactly where to focus next.

Instructions: 1. Close all notes, the module README, and any reference materials. 2. Set a timer. Note your start time below. 3. Attempt every question — partial credit exists. 4. After finishing, grade yourself using ANSWERS.md. 5. Record your score in the Grading Record at the bottom.

Start time: ___________ End time: ___________ Total time: ___________

Scoring Table¶

Passing score: 15/22 (68%)  ·  Target score: 18/22 (82%)

Section 1: Recall (5 questions × 1 pt = 5 pts)¶

Quick recall questions. Answer from memory in 1–3 sentences each.

1.1 What is the http.Handler interface? Write its method signature from memory.

Your answer:

1.2 In Go 1.22, what is the pattern string syntax for registering a route that handles only GET requests to /items/{id}? What function do you call inside the handler to retrieve the value of id?

Your answer:

1.3 When must you call w.Header().Set("Content-Type", "application/json") relative to calling w.WriteHeader(status) or writing the body? Why?

Your answer:

1.4 What is the role of http.MaxBytesReader? What error type does it produce when the limit is exceeded, and how do you detect it?

Your answer:

1.5 Name the three timeout fields on http.Server that you should always configure in production, and briefly describe what each one covers.

Your answer:

Section 2: Conceptual Understanding (3 questions × 2 pts = 6 pts)¶

Demonstrate that you understand the "why", not just the "what".

2.1 Explain the middleware pattern in Go. What is the signature of a middleware function? Walk through how WithLogging(WithRequestID(mux)) creates a middleware chain, and explain in what order the "before" and "after" phases of each middleware execute relative to the handler.

Your answer:

2.2 Explain why a production service should configure an explicit http.Server struct rather than using http.ListenAndServe(addr, handler) directly. Cover at least two concrete risks of using http.ListenAndServe without timeout configuration.

Your answer:

2.3 Describe the graceful shutdown sequence using signal.NotifyContext and srv.Shutdown(ctx). What does srv.Shutdown do that distinguishes it from simply killing the process? Why do you need a fresh context (not the signal context) for the shutdown call?

Your answer:

Section 3: Applied / Practical (2 questions × 3 pts = 6 pts)¶

Show that you can use your knowledge to solve real problems.

3.1 Write a complete Go function handleCreateProduct(w http.ResponseWriter, r *http.Request) that: - Limits the request body to 256 KB - Decodes a JSON body into a struct with name string (required) and price float64 (must be > 0) - Returns appropriate JSON error responses for: empty body (400), invalid JSON (400), missing name (422), non-positive price (422) - On success returns 201 Created with the decoded struct as JSON - Sets Content-Type: application/json on all responses

You may define any helper types or functions you need.

Your answer:

3.2 Write a TestHandleCreateProduct test function using httptest.NewRecorder and httptest.NewRequest that covers at least four distinct cases (valid input, empty body, missing name, non-positive price). Use table-driven test structure.

Your answer:

Section 4: Scenario / Debugging (1 question × 3 pts = 3 pts)¶

Analyze a realistic scenario and identify what's wrong or what should be done.

4.1 A colleague writes the following handler and notices that clients sometimes receive garbled responses — the body is correct JSON but the HTTP status code is always 200, even when an error occurred. They also notice that Content-Type is sometimes missing from the response. Identify all bugs, explain why each one causes the observed symptom, and rewrite the handler correctly.

func getUser(w http.ResponseWriter, r *http.Request) {
    id := r.PathValue("id")
    user, err := userStore.Get(r.Context(), id)
    if err != nil {
        w.WriteHeader(http.StatusNotFound)
        w.Header().Set("Content-Type", "application/json")
        json.NewEncoder(w).Encode(map[string]string{"error": "user not found"})
    }
    w.Header().Set("Content-Type", "application/json")
    json.NewEncoder(w).Encode(user)
}

a) Identify and explain every bug.

b) Rewrite the handler correctly.

Your answer:

Section 5: Essay / Discussion (1 question × 2 pts = 2 pts)¶

Open-ended. There is more than one good answer. Show your reasoning.

5.1 "With Go 1.22, you no longer need a third-party router for most Go services." Evaluate this claim. Describe at least two scenarios where the Go 1.22 stdlib mux is sufficient and at least two scenarios where you might still reach for a third-party router such as chi or gin. What is the cost of each choice?

Your answer (aim for 4–8 sentences):

Section 6: Bonus Challenge (1 question × +5 pts)¶

[!NOTE] This question is optional. It will not count against you if you skip it or get it wrong. Only attempt it after completing Sections 1–5.

6.1 Write a statusRecorder type that wraps http.ResponseWriter and captures the HTTP status code written by a handler. Implement: - The statusRecorder struct with an embedded http.ResponseWriter and an integer code field - A WriteHeader(code int) method that stores the code and delegates to the embedded writer - A Write(b []byte) method that sets code to 200 (the implicit default) if WriteHeader was never called, then delegates

Then write a WithLogging middleware that uses statusRecorder to log METHOD /path STATUS duration (e.g., GET /items/1 200 142µs) after every request.

Include a test showing that: a 404-returning handler produces a log entry with 404, and a 200-returning handler produces a log entry with 200.

Your answer:

Self-Assessment¶

After grading your test, answer these questions honestly:

What did I get right and why?

Your reflection:

What did I get wrong and why did I make that mistake?

Your reflection:

What should I review before moving to the next module?

Your reflection:

What score did I get? Do I feel it accurately reflects my understanding?

Your reflection:

Grading Record¶

Append a new row each time you take this test. Do not overwrite previous attempts.

Grade scale: A ≥ 90% (≥20/22)  ·  B ≥ 80% (≥18/22)  ·  C ≥ 70% (≥15/22)  ·  D ≥ 60% (≥13/22)  ·  F < 60%

See ANSWERS.md for the answer key. Review it only after completing the test.