> For the complete documentation index, see [llms.txt](https://ineelhere.gitbook.io/code-with-go/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ineelhere.gitbook.io/code-with-go/41-mutexes.md).

# Mutexes

This Go code illustrates the use of a mutex (Mutual Exclusion) to safely increment counters in a concurrent environment. Here's an explanation with inline comments:

```go
package main

import (
	"fmt"
	"sync"
)

// Container represents a structure with a mutex-protected map of counters.
type Container struct {
	mu       sync.Mutex
	counters map[string]int
}

// inc increments the counter for a given name, protected by a mutex.
func (c *Container) inc(name string) {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.counters[name]++
}

func main() {
	// Initializing a Container with counters for names "a" and "b"
	c := Container{
		counters: map[string]int{"a": 0, "b": 0},
	}

	var wg sync.WaitGroup

	// doIncrement is a function that increments a counter 'n' times for a given name.
	doIncrement := func(name string, n int) {
		for i := 0; i < n; i++ {
			c.inc(name)
		}
		wg.Done()
	}

	// Launching three goroutines to increment counters concurrently.
	wg.Add(3)
	go doIncrement("a", 10000)
	go doIncrement("a", 10000)
	go doIncrement("b", 10000)

	// Waiting for all goroutines to finish.
	wg.Wait()

	// Printing the final counters.
	fmt.Println(c.counters)
}
```

#### Output

```
map[a:20000 b:10000]
```

Explanation:

1. `Container` struct: It includes a mutex (`mu`) and a map of counters (`counters`).
2. `inc` method: It increments the counter for a given name, using a mutex (`mu`) to protect concurrent access.
3. In the `main` function:
   * An instance of `Container` (`c`) is created with counters initialized for names "a" and "b".
   * The `doIncrement` function is defined to increment a counter 'n' times for a given name. It uses `c.inc` to safely increment counters.
   * Three goroutines are launched concurrently to increment counters for names "a" and "b".
   * The `sync.WaitGroup` (`wg`) is used to wait for all goroutines to finish before proceeding.
   * The final counters are printed.

Using a mutex ensures that the `inc` method is executed atomically, preventing race conditions that might occur when multiple goroutines attempt to modify the counters concurrently. This approach ensures the correctness and safety of the concurrent counter increments.