| The primary mechanism for managing state in Go is communication over channels. We saw this for example with [worker pools](worker-pools). There are a few other options for managing state though. Here we'll look at using the `sync/atomic` package for _atomic counters_ accessed by multiple goroutines. | ||
package main |
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import ( |
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"fmt" |
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"sync" |
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"sync/atomic" |
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) |
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func main() { |
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| We'll use an unsigned integer to represent our (always-positive) counter. | var ops uint64 |
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| A WaitGroup will help us wait for all goroutines to finish their work. | var wg sync.WaitGroup |
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| We'll start 50 goroutines that each increment the counter exactly 1000 times. | for i := 0; i < 50; i++ { |
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wg.Add(1) |
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go func() { |
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for c := 0; c < 1000; c++ { |
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| To atomically increment the counter we use `AddUint64`, giving it the memory address of our `ops` counter with the `&` syntax. | atomic.AddUint64(&ops, 1) |
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} |
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wg.Done() |
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}() |
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} |
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| Wait until all the goroutines are done. | wg.Wait() |
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| It's safe to access `ops` now because we know no other goroutine is writing to it. Reading atomics safely while they are being updated is also possible, using functions like `atomic.LoadUint64`. | fmt.Println("ops:", ops) |
ops: 50000 |
} |