bench.go

package main

import (
        "fmt"
        "net/http"
        "sync"
        "time"
)

func foo(w http.ResponseWriter, r *http.Request) {
        fmt.Fprint(w, []byte(`hello world`))
}

func call(i int, wg *sync.WaitGroup){
    defer wg.Done()

    for j := 0; j < i; j++ {
        _, err := http.Get("http://localhost:9099")
        if err != nil {
            fmt.Println("call err: ", err)
            return
        }
    }
}

func main() {
        http.HandleFunc("/", foo)
        go http.ListenAndServe(":9099", nil)

        wg := new(sync.WaitGroup)

        var start, stop int
        start = time.Now().Nanosecond()
        fmt.Println("\n--- Call example ---\n")
        wg.Add(5)
        go call(10000, wg)
        go call(10000, wg)
        go call(10000, wg)
        go call(10000, wg)
        go call(10000, wg)
        wg.Wait()
        stop = time.Now().Nanosecond()
        println("Call example Time used: ", stop-start)
}

If try to use net/http client.Get("http://localhost:9099") to replace http.Get("http://localhost:9099"), can avoid the error: "call err: Get http://localhost:9099: dial tcp [::1]:9099: socket: too many open files"

net/http client.Get/Post can utilize net/http transport.go Transport connection pool.