update readme

README.md

@@ -10,3 +10,64 @@
 - Automatic scaling Number of routines by the number of tasks.
 - Support waiting all tasks finished.
 - Panic in tasks will be recovered.
+
+### Usages
+
+Write a http benchmark tool with routinepool, calculate the average time of each request.
+```
+package main
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/icefed/routinepool"
+)
+
+func main() {
+	p := routinepool.NewPool(routinepool.WithMaxWorkers(8))
+	p.StartN(8)
+
+	var errCount int32
+	client := &http.Client{
+		Transport: &http.Transport{
+			MaxConnsPerHost: 12,
+		},
+	}
+	costs := make([]time.Duration, 0)
+	mu := sync.Mutex{}
+
+	f := func() {
+		start := time.Now()
+		defer func() {
+			mu.Lock()
+			defer mu.Unlock()
+			costs = append(costs, time.Since(start))
+		}()
+		req, _ := http.NewRequest("GET", "http://localhost:8099/hello", nil)
+		resp, err := client.Do(req)
+		io.Copy(io.Discard, resp.Body)
+		if err != nil {
+			atomic.AddInt32(&errCount, 1)
+			return
+		}
+		resp.Body.Close()
+	}
+	for i := 0; i < 100000; i++ {
+		p.AddTask(f)
+	}
+	p.Wait()
+
+	avg := time.Duration(0)
+	total := time.Duration(0)
+	for _, cost := range costs {
+		total += cost
+	}
+	avg = total / time.Duration(len(costs))
+	fmt.Printf("total requests: %d, avg cost: %s, err count: %d\n", len(costs), avg, errCount)
+}
+```

pool.go

@@ -66,7 +66,7 @@ func NewPool(opts ...Option) *Pool {
 }
 
 // Start start routine pool in background.
-// The initial number of workers is determined by the number of tasks in the channel.
+// The initial number of workers is determined by the number of tasks in the channel and maxWorkers.
 func (p *Pool) Start() {
 	p.start(min(len(p.taskChan), p.maxWorkers))
 }