Go で同時 HTTP リクエストを効率的に処理するにはどうすればよいですか?

net/http: Request.Body is closed

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

// Default values
var (
    reqs        = 1000000
    maxWorkers  = 200
    sem         = make(chan bool, maxWorkers)
    respChan    = make(chan *http.Response)
    respErrChan = make(chan error)
)

func main() {
    runtime.GOMAXPROCS(runtime.NumCPU())

    // Dispatcher: sends requests to the worker pool
    go func() {
        for i := 0; i < reqs; i++ {
            sem <- true
            req, err := http.NewRequest(http.MethodGet, "http://localhost:8080", nil)
            if err != nil {
                respErrChan <- err
                return
            }
            client := &http.Client{Timeout: 15 * time.Second}
            resp, err := client.Do(req)
            if err != nil {
                respErrChan <- err
                return
            }
            respChan <- resp
        }
        close(sem)
        close(respChan)
    }()

    // Worker Pool: sends requests to the API
    var wg sync.WaitGroup
    for i := 0; i < maxWorkers; i++ {
        wg.Add(1)
        go func() {
            defer wg.Done()
            for {
                select {
                case resp := <-respChan:
                    fmt.Println(resp.Status)
                    resp.Body.Close()
                    sem <- true
                case err := <-respErrChan:
                    log.Fatal(err)
                }
            }
        }()
    }

    wg.Wait()
}