How to periodically update and refresh expvar variables in a Go application?

In a Go application, you can periodically update and refresh expvar variables by using a combination of goroutines and a ticker.

Here's an example code that demonstrates how to achieve this:

package main

import (
	"expvar"
	"time"
)

func updateExpvarVariable() {
	// Create a ticker to periodically update the expvar variable
	ticker := time.NewTicker(time.Second * 5)

	for {
		select {
		case <-ticker.C:
			// Update the expvar variable here
			// Replace "myVar" with the name of your expvar variable
			expvar.Get("myVar").(*expvar.Int).Add(1)
		}
	}
}

func main() {
	// Initialize your expvar variable here
	// Replace "myVar" with the name of your expvar variable
	expvar.NewInt("myVar").Set(0)

	// Start updating the expvar variable in a separate goroutine
	go updateExpvarVariable()

	// Start your application logic here

	// Keep the main goroutine alive
	select {}
}

In this example, we create a ticker that triggers every 5 seconds. Inside the updateExpvarVariable function, we update the expvar variable by using a type assertion (expvar.Get("myVar").(*expvar.Int)) to get the variable as a specific type (in this case, expvar.Int). You can replace expvar.Int with the appropriate type for your variable.

Make sure to initialize your expvar variable before starting the update goroutine. In the main function, we initialize the variable with an initial value of 0, but you should replace it with the appropriate initialization for your variable.

The main goroutine is kept alive using a select {} statement to prevent the program from exiting.