How to access and view expvar statistics in a Go application during runtime?

To access and view expvar statistics in a Go application during runtime, you can follow these steps:

1. Import the expvar package in your Go application.

   import "expvar"

2. Register your expvar variables by calling expvar.Publish or expvar.NewXXX functions. For example:

   var counter = expvar.NewInt("counter")

3. Expose the expvar HTTP endpoint by adding the expvar.Handler() to your HTTP router or server. For example:

   http.Handle("/debug/vars", expvar.Handler())

4. Start your Go application and ensure it's running.

5. Open a web browser and navigate to http://localhost:port/debug/vars, where port is the port number your Go application is running on.

6. You will see a JSON representation of the expvar variables registered in your application, including their current values.

You can also use command-line tools like curl to view expvar statistics during runtime. For example:

This will output the expvar statistics on the command line.

By accessing and viewing the expvar statistics, you can monitor the runtime behavior of your Go application and obtain useful information about its performance and internal state.