1.simplify reading and writing file code

2.add apiauth test

plugins/apiauth/apiauth_test.go

@@ -0,0 +1,20 @@
+package apiauth
+
+import (
+	"net/url"
+	"testing"
+)
+
+func TestSignature(t *testing.T) {
+	appsecret := "beego secret"
+	method := "GET"
+	RequestURL := "http://localhost/test/url"
+	params := make(url.Values)
+	params.Add("arg1", "hello")
+	params.Add("arg2", "beego")
+
+	signature := "mFdpvLh48ca4mDVEItE9++AKKQ/IVca7O/ZyyB8hR58="
+	if Signature(appsecret, method, params, RequestURL) != signature {
+		t.Error("Signature error")
+	}
+}