Avoid mutexes on channels

Go pattern

Detected a channel guarded with a mutex. Channels already have an internal mutex, so this is unnecessary. Remove the mutex.

references

Channel guarded with mutex

BEFORE
package main

import (
	"fmt"
	"sync"
)

func main() {
	var wg sync.WaitGroup
	var mu sync.Mutex
	channel := make(chan int)

	// Producer
	wg.Add(1)
	go func() {
		defer wg.Done()
		for i := 0; i < 5; i++ {
			mu.Lock()
			channel <- i
			mu.Unlock()
		}
		close(channel)
	}()

	// Consumer
	wg.Add(1)
	go func() {
		defer wg.Done()
		for num := range channel {
			mu.Lock()
			fmt.Println(num)
			mu.Unlock()
		}
	}()

	wg.Wait()
}
AFTER
package main

import (
	"fmt"
	"sync"
)

func main() {
	var wg sync.WaitGroup
	channel := make(chan int)

	// Producer
	wg.Add(1)
	go func() {
		defer wg.Done()
		for i := 0; i < 5; i++ {
			channel <- i
		}
		close(channel)
	}()

	// Consumer
	wg.Add(1)
	go func() {
		defer wg.Done()
		for num := range channel {
			fmt.Println(num)
		}
	}()

	wg.Wait()
}

Without Channel guarded with mutex

GO
package main

import (
	"fmt"
	"sync"
)

func main() {
	var wg sync.WaitGroup
	var mu sync.Mutex
	data := make([]int, 0)

	// Producer
	wg.Add(1)
	go func() {
		defer wg.Done()
		for i := 0; i < 5; i++ {
			mu.Lock()
			data = append(data, i)
			mu.Unlock()
		}
	}()

	// Consumer
	wg.Add(1)
	go func() {
		defer wg.Done()
		mu.Lock()
		for _, num := range data {
			fmt.Println(num)
		}
		mu.Unlock()
	}()

	wg.Wait()
}