12. Short Q&A Prompts (Practice)

Quick drills to reinforce fundamentals and improve clarity under time pressure.

• What does go test -race detect, and when should you run it?
• Who should close a channel, and how do receivers detect closure?
• When do you choose sync.RWMutex over sync.Mutex?
• What’s the difference between nil and empty slices in JSON?
• How do go.mod and go.sum work together?
• Why is map iteration order not deterministic, and how to make it stable?
• When should you use context.Context, and how do you propagate it?
• How do you wait for multiple goroutines to finish?
• What’s the difference between new and make?
• How do you format time as RFC3339 and YYYY-MM-DD in Go?

Extra drills

• How do you configure an http.Client with timeouts and a custom Transport?
• Show the comma-ok idiom for map lookup and type assertion.
• Write a select with ctx.Done() timeout and a default case.
• Demonstrate flag parsing for -port and -env with defaults.