Go: Read/Write variable locking - demo of Read locking without block with slow Write lock

rwmutex-no-blocking.go

package main

import (
	"fmt"
	"sync"
	"time"
)

type C struct {
	sync.RWMutex
	i     int
	files []string
}

type A struct {
	sync.Mutex
	c *C
}

func (c *C) Init() {
	c.Lock()
	c.files = make([]string, 0)
	for i := c.i; i < c.i+5; i++ {
		c.files = append(c.files, fmt.Sprintf("file%d", i))
		time.Sleep(time.Microsecond * 500)
	}
	c.i += 5
	c.Unlock()
}

func (c *C) GetFiles() []string {
	c.RLock()
	defer c.RUnlock()
	return c.files
}

func (a *A) loadConfiguration() {
	c := *a.c
	c.Init()
	a.Lock()
	a.c = &c
	a.Unlock()
}

func main() {

	app := &A{
		c: &C{},
	}
	app.loadConfiguration()

	go func() {
		ticker := time.NewTicker(time.Second * 5)
		for {
			select {
			case <-ticker.C:
				app.loadConfiguration()
			}
		}
	}()

	wait := make(chan bool, 1)

	go func() {
		ticker := time.NewTicker(time.Second * 1)
		for {
			select {
			case <-ticker.C:
				fmt.Println("app.c.GetFiles>>", app.c.GetFiles())
			}
		}
	}()

	go func() {
		ticker := time.NewTicker(time.Second * 1)
		for {
			select {
			case <-ticker.C:
				fmt.Println("app.c.files>>", app.c.files)
			}
		}
	}()

	<-wait
}