Refactor error into its own struct

client.go

@@ -138,6 +138,9 @@ func (o *Client) UploadFiles(ctx context.Context, rs []NamedReader) (response *R
 	if err != nil {
 		return
 	}
+	if !response.Success {
+		return nil, &ErrUploadFailed{response.Description, response.Errorcode}
+	}
 
 	return
 }

response.go

@@ -21,6 +21,8 @@
 
 package owo
 
+import "fmt"
+
 type (
 	// Response contains json marshalled response from owo
 	Response struct {
@@ -40,8 +42,18 @@ type (
 		Errorcode   int    `json:"errorcode,omitempty"`
 		Description string `json:"description,omitempty"`
 	}
+
+	// ErrUploadFailed thrown when success flag on response is false
+	ErrUploadFailed struct {
+		Message   string
+		ErrorCode int
+	}
 )
 
+func (e ErrUploadFailed) Error() string {
+	return fmt.Sprintf("Upload failed with code %d and message '%s'", e.ErrorCode, e.Message)
+}
+
 // WithCDN returns file url prefixed with the CDN
 func (f File) WithCDN(cdn string) string {
 	return cdn + f.URL