You're supposed to do Add(1) -> Wait; and you'd normally wait once, in a
single goroutine. Typical pattern:
wg.Add(1)
go func() {
defer wg.Done()
... foo
}
wg.Add(1)
go func() {
defer wg.Done()
... bar
}
wg.Wait() // wait for both goroutines to complete
On Tuesday, 17 January 2023 at 04:56:44 UTC bodqh...@gmail.com wrote:
The goroutine has a Wait -> Add(1) -> Done chain.
*Inside* a goroutine? That sounds problematic and racy, as you've found.
- you're Waiting on the same waitgroup in multiple goroutines
concurrently? Then when it counts to zero, multiple goroutines would be
able to start to run
- you're re-adding to a waitgroup even after it's counted down to zero?
That means that "wait" is non-deterministic (it may miss a count down to
zero and back up again).
It sounds to me like you need some other synchronization primitive, but I
don't know what it is you're trying to do. Possibly a semaphore.
This video is well worth watching, several times:
https://www.youtube.com/watch?v=5zXAHh5tJqQ
This opened my eyes to a very useful pattern:
- have a one-item buffered channel
- push a value into that channel
- whenever you want to use it: pop it out, use it, and push the updated
value back in
This is a very simple and clean way of doing what would otherwise require a
mutex to protect.
Maybe also useful:
https://www.youtube.com/watch?v=f6kdp27TYZs
https://www.youtube.com/watch?v=oV9rvDllKEg
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