add example

examples/parallel_request.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+
+	"git.tuxpa.in/a/lambda/parallel"
+)
+
+type someResult struct {
+	Title string `json:"title"`
+	Id    int    `json:"id"`
+}
+
+func main() {
+	var requests = make([]*http.Request, 20)
+
+	for i := range requests {
+		r, _ := http.NewRequest("GET", fmt.Sprintf("https://jsonplaceholder.typicode.com/todos/%d", i), nil)
+		requests[i] = r
+	}
+
+	results, errs := parallel.MapErrorV(requests, func(r *http.Request) (*someResult, error) {
+		out := &someResult{}
+		res, err := http.DefaultClient.Do(r)
+		if err != nil {
+			return nil, err
+		}
+		defer res.Body.Close()
+		err = json.NewDecoder(res.Body).Decode(out)
+		return out, err
+	}, 4)
+
+	for i, v := range results {
+		if errs[i] != nil {
+			log.Printf("err: %s", errs[i])
+		} else {
+			log.Printf("result: %+v", v)
+		}
+	}
+}