Go Concurrency Patterns Checkpoint

Structured concurrency, cancellation, backpressure, and safe publication.

Get every question correct to pass this checkpoint. You can review feedback, revise your answers, and submit again.

1. BoundMap computes inputs [7,3,8] and the callbacks finish at indices 2,0,1. Each returns its input plus 10. What output is required?

Select one answer.

[17,13,18] [18,17,13] [13,17,18] Any permutation because execution is concurrent

2. Each new goroutine acquires a semaphore inside its body before calling fn. For a million inputs and limit 4, what is actually bounded?

Select one answer.

The total number of goroutines ever created is four Concurrent fn calls, but potentially not the number of waiting goroutines The output automatically has at most four elements The producer cannot submit more than four jobs

3. A producer has finished sending jobs to workers that range over a channel. It calls Wait before closing jobs. What can happen?

Select one answer.

Wait automatically closes every worker channel Workers exit because a sender is not currently active The channel discards all pending jobs Workers wait for another job while the producer waits for their exit

4. A context-aware worker has both a ready job and a ready ctx.Done case in select. Which behavior is guaranteed?

Select one answer.

Cancellation always wins because it is a context The first textual case always wins Either ready communication may be selected The job always wins because it arrived first

5. One callback blocks forever on a channel unrelated to context. The parent cancels and joins all workers. What should the caller expect?

Select one answer.

Cancel forcibly terminates the callback goroutine The callback must return the zero value automatically WaitGroup interrupts blocking channel receives The join can remain blocked because the callback does not cooperate

6. BoundMap receives nonempty input, a valid callback, and maxConcurrency=-1. What value must it return without invoking the callback?

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