30a235b655
* docs: remove typo * Update mutexes.go * feat: add changes Co-authored-by: Javier Pacareu <jpacareu.meli@gmail.com>
63 lines
1.5 KiB
Go
63 lines
1.5 KiB
Go
// In the previous example we saw how to manage simple
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// counter state using [atomic operations](atomic-counters).
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// For more complex state we can use a [_mutex_](https://en.wikipedia.org/wiki/Mutual_exclusion)
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// to safely access data across multiple goroutines.
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package main
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import (
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"fmt"
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"sync"
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)
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// Container holds a map of counters; since we want to
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// update it concurrently from multiple goroutines, we
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// add a `Mutex` to synchronize access.
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// Note that mutexes must not be copied, so if this
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// `struct` is passed around, it should be done by
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// pointer.
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type Container struct {
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mu sync.Mutex
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counters map[string]int
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}
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func (c *Container) inc(name string) {
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// Lock the mutex before accessing `counters`; unlock
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// it at the end of the function using a [defer](defer)
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// statement.
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c.mu.Lock()
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defer c.mu.Unlock()
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c.counters[name]++
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}
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func main() {
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c := Container{
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// Note that the zero value of a mutex is usable as-is, so no
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// initialization is required here.
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counters: map[string]int{"a": 0, "b": 0},
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}
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var wg sync.WaitGroup
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// This function increments a named counter
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// in a loop.
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doIncrement := func(name string, n int) {
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for i := 0; i < n; i++ {
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c.inc(name)
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}
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wg.Done()
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}
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// Run several goroutines concurrently; note
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// that they all access the same `Container`,
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// and two of them access the same counter.
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wg.Add(3)
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go doIncrement("a", 10000)
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go doIncrement("a", 10000)
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go doIncrement("b", 10000)
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// Wait for the goroutines to finish
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wg.Wait()
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fmt.Println(c.counters)
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}
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