expvar 简单使用

Package expvar provides a standardized interface to public variables, such as operation counters in servers. It exposes these variables via HTTP at /debug/vars in JSON format.

In addition to adding the HTTP handler, this package registers the following variables:

cmdline   os.Args
memstats  runtime.Memstats

The package is sometimes only imported for the side effect of registering its HTTP handler and the above variables. To use it this way, link this package into your program:

导入包就是使用了, 会自动添加一个**/debug/vars**的http 服务, 具体实现看源码, 很简单,

有一个多线程 map读写锁的实现

import _ "expvar"

一个简单的http:

package main

import (
	"expvar"
	"net/http"
	"time"
)

func testData() any {
	return "hello expvar"
}

func main() {
	test := expvar.NewMap("Test")
	test.Add("go", 10)
	test.Add("go1", 10)
	aliveOfSeconds := expvar.NewInt("aliveOfSeconds")
	expvar.NewString("TestString").Set("this is a test string")
	expvar.Publish("TestFunc", expvar.Func(testData))
	go http.ListenAndServe(":8080", nil)
	for {
		aliveOfSeconds.Add(1)
		time.Sleep(1 * time.Second)
	}
}