How to reset or zero out expvar variables at specific intervals in Go?

To reset or zero out expvar variables at specific intervals in Go, you can use time.Ticker along with a sync.Mutex. Here's an example:

package main

import (
	"expvar"
	"sync"
	"time"
)

var (
	myVar *expvar.Int
	mu    sync.Mutex
)

func main() {
	myVar = expvar.NewInt("myVar")

	// Run the reset function every 5 seconds
	resetInterval := 5 * time.Second
	ticker := time.NewTicker(resetInterval)
	defer ticker.Stop()

	go func() {
		for range ticker.C {
			resetExpVar()
		}
	}()

	// To simulate long-running code
	for {
		time.Sleep(1 * time.Second)
		myVar.Add(1)
	}
}

func resetExpVar() {
	mu.Lock()
	defer mu.Unlock()

	myVar.Set(0)
}

In this example, we use expvar.NewInt() to create an expvar integer variable called myVar. We also define a mutex mu to synchronize access to the variable.

We then create a time.Ticker that ticks every 5 seconds and runs the resetExpVar() function. Inside the resetExpVar() function, we acquire the lock using mu.Lock() to ensure exclusive access to myVar, reset its value using myVar.Set(0), and release the lock using mu.Unlock().

Finally, inside the main loop, we add 1 to myVar every second to simulate events or updates, while the resetExpVar() function periodically resets the value to 0.