added tests

updated go version and packages

generator/plain_test.go

@@ -0,0 +1,16 @@
+package generator
+
+import "testing"
+
+func TestGenerator_GenerateUrl(t *testing.T) {
+	g, err := NewGenerator(Config{})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	url, _ := g.generatePlainUrl("local:///test.png")
+
+	if url != "plain/local:///test.png" {
+		t.Errorf("url is %s", url)
+	}
+}