Update go.mod and add Unit Test

go.mod

@@ -1,4 +1,4 @@
-module github.com/Nv7-Github/screenshot
+module github.com/kbinani/screenshot
 
 go 1.16
 

screenshot_test.go

@@ -0,0 +1,24 @@
+package screenshot
+
+import (
+	"testing"
+)
+
+func TestCaptureRect(t *testing.T) {
+	bounds := GetDisplayBounds(0)
+	_, err := CaptureRect(bounds)
+	if err != nil {
+		t.Error(err)
+	}
+}
+
+func BenchmarkCaptureRect(t *testing.B) {
+	bounds := GetDisplayBounds(0)
+	t.ResetTimer()
+	for i := 0; i < t.N; i++ {
+		_, err := CaptureRect(bounds)
+		if err != nil {
+			t.Error(err)
+		}
+	}
+}