🧩 Exercises – HTTP Services in Go

These exercises are designed to help you practice building HTTP services step by step. Start simple and gradually move toward more realistic backend scenarios.

---

🎯 Exercise Guidelines

• Write clean and readable code
• Handle errors explicitly
• Use proper HTTP status codes
• Keep handlers small and focused
• Write tests wherever applicable

---

🟢 Level 1 – Basics (Warm-up)

Exercise 1: Hello Endpoint

Create an endpoint:

GET /hello

Requirements:

• Return: "Hello, Go HTTP!"
• Status: 200 OK

---

Exercise 2: Method Validation

Enhance /hello:

• Allow only GET
• Return 405 Method Not Allowed for others

---

Exercise 3: Custom Handler

Create a custom struct that implements:

```go id=”ex3” ServeHTTP(w http.ResponseWriter, r *http.Request)

Use it for a new route:

```id="ex3route"
/custom

---

🟡 Level 2 – JSON Handling

Exercise 4: JSON Response

Create:

/user

Return JSON:

{
  "name": "Aditya",
  "role": "Developer"
}

Requirements:

• Set correct Content-Type
• Use json.NewEncoder

---

Exercise 5: JSON Request Parsing

Create:

POST /echo

Requirements:

• Accept JSON input
• Return the same JSON back
• Handle invalid JSON properly

---

Exercise 6: Validation

Enhance /echo:

• Reject empty fields
• Return 400 Bad Request with message

---

🟠 Level 3 – Middleware

Exercise 7: Logging Middleware

Create middleware that logs:

• HTTP method
• Request path

Apply it to at least one endpoint.

---

Exercise 8: Header Middleware

Create middleware that:

• Adds a custom header:

  X-App-Version: 1.0
  

---

Exercise 9: Middleware Chaining

Chain multiple middleware:

• Logging + Header middleware

---

🔵 Level 4 – Real API Patterns

Exercise 10: Health Check API

Create:

/health

Return:

• Status: 200 OK

• JSON:

  { "status": "UP" }
  

---

Exercise 11: User Creation API

Create:

POST /users

Requirements:

• Accept JSON input (name, age)
• Return success message
• Validate input
• Return appropriate status codes

---

Exercise 12: Error Handling

Enhance /users:

• Return meaningful error messages
• Handle malformed JSON
• Handle missing fields

---

🔴 Level 5 – Advanced & Production Thinking

Exercise 13: Context Timeout

• Add a timeout to a handler
• Simulate a slow operation
• Return timeout error if exceeded

---

Exercise 14: Graceful Shutdown

Modify your server:

• Handle OS interrupt
• Shutdown cleanly

---

Exercise 15: Refactoring for Testability

Refactor your handlers:

• Remove business logic from HTTP layer
• Use interfaces for dependencies

---

🧪 Bonus Exercises (Optional but Recommended)

Exercise 16: Table-Driven Testing

• Write table-driven tests for /echo

---

Exercise 17: HTTP Status Coverage

Ensure your APIs correctly use:

• 200, 201, 400, 404, 500

---

Exercise 18: Simple Router Abstraction

• Create a small wrapper around http.ServeMux
• Organize routes cleanly

---

🧠 Reflection Questions

• What makes a handler “clean” in Go?
• How does Go’s approach differ from Python frameworks?
• Where should business logic live?

---

📌 Key Takeaway

“Practice is where Go starts to feel natural.”

These exercises are designed to move you from:

• Writing handlers ❌ to
• Designing real backend services ✅

---