the big refactor

internal/errors/errors.go

@@ -0,0 +1,25 @@
+package s3browser
+
+import "fmt"
+
+type ExtendedError struct {
+	Message string
+	Code    string
+}
+
+func (err *ExtendedError) Error() string {
+	return err.Message
+}
+
+func (err *ExtendedError) Extensions() map[string]interface{} {
+	return map[string]interface{}{
+		"code": err.Code,
+	}
+}
+
+func ExtendError(code, format string, a ...interface{}) *ExtendedError {
+	return &ExtendedError{
+		Message: fmt.Sprintf(format, a...),
+		Code:    code,
+	}
+}