add README

Author: neoql

README.md

@@ -0,0 +1,61 @@
+# workerpool
+
+Concurrency limiting goroutine pool.
+
+## Install
+
+```
+go get -v github.com/neoql/workerpool
+```
+
+## Example
+
+```go
+package main
+
+import (
+    "fmt"
+    "time"
+    "sync"
+
+    "github.com/neoql/workerpool"
+)
+
+func main() {
+    var wg sync.WaitGroup
+
+    fn := func(argv workerpool.Argv) {
+        no := argv.(int)
+        fmt.Printf("fn-%d enter...\n", no)
+        time.Sleep(time.Second*3)
+        fmt.Printf("fn-%d exit.\n", no)
+        wg.Done()
+    }
+
+    pool := workerpool.New(2, time.Second*1)
+
+    wg.Add(3)
+    for i := 0; i < 3; i++ {
+        if !pool.Spawn(fn, i) {
+            fmt.Printf("launch fn-%d failed, WorkerPool is full", i)
+            fmt.Println("Waiting for an empty position")
+            pool.WaitSpawn(fn, i)
+        }
+    }
+
+    wg.Wait()
+}
+```
+```
+fn-0 enter...
+fn-1 enter...
+launch fn-2 failed, WorkerPool is fullWaiting for an empty position
+fn-1 exit.
+fn-0 exit.
+fn-2 enter...
+fn-2 exit.
+```
+
+## License
+
+MIT, read more [here](./LICENSE).