A web server that announces whether or not a particular Go version has been tagged.
There are two problems here if you look carefully at main_test.go
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Race Condition Problem. A and B are trying to access the same resource, one of the access is WRITE.
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Rendezvous Problem. The need to ensure the order of executions. A cannot happen before B.
If you study carefully enough, these are actually concurrency problem, how do I
know? Easy, there is go routine in it.
Concurrency problems are hard to solve by nature, and it always boils down to
one evil root-cause: they are non-deterministic.
Now you know the root cause, to solve any kind of concurrency problems, it easy,
you just need to make them deterministic again. The hard part is, HOW?
It turns out that, concurrency primitive of Go: channel is pretty good at solving
these type of problems. Just like sleep(), it blocks.
General techniques in solving concurrency problem:
- Signal. guarantees order of execution by communications
- Guard. guarantees number of simultaneous access & order, too
The two Problems described above is solved using technique#1, signaling.