diff --git a/.gitignore b/.gitignore
index ec6c7f9..cb60bc9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,3 +16,6 @@
 
 # IDE directories
 .idea/
+
+# Output files
+out.json
diff --git a/export.go b/export.go
index c36a48f..9cd50d6 100644
--- a/export.go
+++ b/export.go
@@ -4,14 +4,21 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"sync"
 )
 
+var file *os.File
+var once sync.Once
+
 func Export(response *Response) {
-	file, err := os.Create("out.json")
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "output file creation error: %v", err)
-		return
-	}
+	once.Do(func() {
+		newFile, err := os.OpenFile("out.json", os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "output file creation error: %v", err)
+			return
+		}
+		file = newFile
+	})
 
 	for res := range response.Exports {
 		//fmt.Println(res)
diff --git a/gezer.go b/gezer.go
index 39cb0d4..f5c72c8 100644
--- a/gezer.go
+++ b/gezer.go
@@ -4,7 +4,9 @@ import (
 	"bytes"
 	"fmt"
 	"github.com/PuerkitoBio/goquery"
+	httpcacheDumb "github.com/fpfeng/httpcache"
 	"io/ioutil"
+	"log"
 	"net/http"
 	"net/url"
 	"os"
@@ -25,9 +27,11 @@ type Opt struct {
 }
 
 func NewGezer(opt Opt) *Gezer {
+	log.SetOutput(os.Stdout)
 	return &Gezer{
 		client: &http.Client{
-			Timeout: time.Second * 10,
+			Timeout:   time.Second * 10,
+			Transport: httpcacheDumb.NewMemoryCacheTransport(),
 		},
 		opt: opt,
 	}
@@ -51,7 +55,7 @@ func (g *Gezer) Get(rawURL string) {
 	}
 
 	// Log
-	fmt.Println("Fetching: ", rawURL)
+	log.Println("Fetching: ", rawURL)
 
 	// Get request
 	resp, err := g.client.Get(rawURL)
@@ -99,17 +103,20 @@ func checkURL(rawURL string, allowedDomains []string) bool {
 	}
 
 	// Check for allowed domains
-	var allowed bool
-	for _, domain := range allowedDomains {
-		if domain == parsedURL.Host {
-			allowed = true
-			break
-		}
-	}
-	if !allowed && len(allowedDomains) != 0 {
-		fmt.Fprintf(os.Stderr, "domain not allowed: %s\n", parsedURL.Host)
+	if len(allowedDomains) != 0 && !Contains(allowedDomains, parsedURL.Host) {
+		log.Printf("Domain not allowed: %s\n", parsedURL.Host)
 		return false
 	}
 
 	return true
 }
+
+// Contains checks whether []string contains string
+func Contains(s []string, e string) bool {
+	for _, a := range s {
+		if a == e {
+			return true
+		}
+	}
+	return false
+}
diff --git a/gezer_test.go b/gezer_test.go
index 4edf82c..2c22753 100644
--- a/gezer_test.go
+++ b/gezer_test.go
@@ -8,9 +8,10 @@ import (
 
 func TestGezer_StartURLs_Simple(t *testing.T) {
 	gezer := NewGezer(Opt{
-		StartURLs: []string{"https://api.ipify.org", "https://api.ipify.org"},
+		StartURLs: []string{"http://api.ipify.org"},
 		ParseFunc: func(r *Response) {
 			fmt.Println(string(r.Body))
+			r.Gezer.Get("http://api.ipify.org")
 		},
 	})
 	gezer.Start()
@@ -42,6 +43,7 @@ func TestGezer_Concurrent_Requests(t *testing.T) {
 		AllowedDomains: []string{"quotes.toscrape.com"},
 		StartURLs:      []string{"http://quotes.toscrape.com/"},
 		ParseFunc: func(r *Response) {
+			//r.Exports <- map[string]interface{}{"href": r.Request.URL.String()}
 			r.Doc.Find("a").Each(func(i int, s *goquery.Selection) {
 				if href, ok := s.Attr("href"); ok {
 					go r.Gezer.Get(r.JoinURL(href))
diff --git a/go.mod b/go.mod
index 146b938..d264ce5 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,7 @@ module github.com/gogezer/gezer
 
 go 1.12
 
-require github.com/PuerkitoBio/goquery v1.5.0
+require (
+	github.com/PuerkitoBio/goquery v1.5.0
+	github.com/fpfeng/httpcache v0.0.0-20181220155740-6b8f16a92be3
+)
diff --git a/go.sum b/go.sum
index 0327c72..c8a6c16 100644
--- a/go.sum
+++ b/go.sum
@@ -2,6 +2,8 @@ github.com/PuerkitoBio/goquery v1.5.0 h1:uGvmFXOA73IKluu/F84Xd1tt/z07GYm8X49XKHP
 github.com/PuerkitoBio/goquery v1.5.0/go.mod h1:qD2PgZ9lccMbQlc7eEOjaeRlFQON7xY8kdmcsrnKqMg=
 github.com/andybalholm/cascadia v1.0.0 h1:hOCXnnZ5A+3eVDX8pvgl4kofXv2ELss0bKcqRySc45o=
 github.com/andybalholm/cascadia v1.0.0/go.mod h1:GsXiBklL0woXo1j/WYWtSYYC4ouU9PqHO0sqidkEA4Y=
+github.com/fpfeng/httpcache v0.0.0-20181220155740-6b8f16a92be3 h1:yoJ3JExhshZwcfvvQLLRqKICf4/p4gZ/mDzdQV1hRWQ=
+github.com/fpfeng/httpcache v0.0.0-20181220155740-6b8f16a92be3/go.mod h1:QThlC5qj7EJa+O2HqbxzVGWLspJQHQLVsKmBtbg9ak8=
 golang.org/x/net v0.0.0-20180218175443-cbe0f9307d01/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20181114220301-adae6a3d119a h1:gOpx8G595UYyvj8UK4+OFyY4rx037g3fmfhe5SasG3U=
 golang.org/x/net v0.0.0-20181114220301-adae6a3d119a/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=