Mutex: Protecting Shared State

The program below starts 100 goroutines. Each one adds 1 to a shared variable 1,000 times, so the final count should be 100,000.

Five runs on one machine printed these totals:

count: 93861
count: 100000
count: 97065
count: 97088
count: 70949
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One run was correct and four were short, the worst by almost 30,000. The program waits for every goroutine with a done channel, as in Waiting for Goroutines with Done Channels, so no goroutine is cut off early. The increments themselves are being lost.