🧪 Exercises – Context, Timeouts & Cancellation

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🎯 Objective

These exercises will help you:

• Understand how context works in real programs
• Practice cancellation and timeouts
• Build intuition for production-grade Go code

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🟢 Level 1 – Basics (Warm-up)

Exercise 1: Basic Context Creation

Create a simple program that:

• Creates a context.Background()
• Passes it to a function
• Prints a message from the function

👉 Goal: Understand how context is passed

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Exercise 2: Manual Cancellation

Write a program where:

• A goroutine runs a loop printing every second
• Use context.WithCancel
• Cancel the context after 3 seconds

👉 Expected: Goroutine should stop gracefully

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Exercise 3: Timeout Context

• Use context.WithTimeout (2 seconds)
• Simulate a task that takes 5 seconds
• Handle timeout properly

👉 Expected output: context deadline exceeded

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🟡 Level 2 – Intermediate

Exercise 4: Respect Cancellation

Write a function:

func longTask(ctx context.Context)

• Runs a loop for 10 iterations
• Each iteration sleeps for 1 second
• Stops early if context is cancelled

👉 Use select with ctx.Done()

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Exercise 5: Context Propagation

Create 3 functions:

• main → service → repository

Pass context through all layers.

👉 Goal:

• Maintain context chain
• No global variables

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Exercise 6: Timeout Wrapper

Write a function:

func executeWithTimeout(parent context.Context)

• Creates a child context with timeout
• Calls another function using this context
• Handles cancellation

👉 Think like a service layer

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🔵 Level 3 – Real-World Scenarios

Exercise 7: Worker with Cancellation

• Create a worker goroutine
• It processes jobs every second
• Stop worker when context is cancelled

👉 Bonus:

• Print “Worker shutting down…”

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Exercise 8: API Simulation

Simulate an API call:

• Function waits for 3 seconds
• If context times out → return error
• Otherwise → return success

👉 Use:

• select
• time.After

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Exercise 9: Multiple Goroutines with Shared Context

• Start 3 goroutines
• All receive same context
• Cancel context after 2 seconds

👉 Expected:

• All goroutines stop together

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🔴 Level 4 – Advanced Thinking

Exercise 10: Prevent Goroutine Leak

Write a function that:

• Starts a goroutine
• Uses context properly
• Ensures no goroutine leak after cancellation

👉 Hint:

• Always listen to ctx.Done()

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Exercise 11: Context + Channel Integration

• Send data through a channel
• Stop processing when context is cancelled

👉 Combine:

• Channels
• Context
• Select

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Exercise 12: HTTP Context Handling (Conceptual + Code)

Write a handler:

func handler(w http.ResponseWriter, r *http.Request)

• Extract context from request
• Pass to a function
• Handle cancellation

👉 Think:

• What happens if client disconnects?

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⭐ Bonus Challenge

Exercise 13: Retry with Context Awareness

Write a retry function:

• Retries operation every second

• Stops retrying if:

  • Success occurs
  • Context is cancelled

👉 This is real production pattern

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🧠 Reflection Questions

After completing exercises, think:

• When should you use context?
• What happens if you ignore ctx.Done()?
• Why is context passed explicitly?
• How is this different from Python?

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🚀 Next Step

👉 Move to Solutions (Only after attempting all exercises)

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