add separator checking and return error

service_a/internal/domains/meteo/file.go

@@ -47,6 +47,10 @@ func (c *CSV) Parse(r io.Reader) ([]MeteoData, []RejectedMeteoData, error) {
 		return nil, nil, fmt.Errorf("%w: %v", ErrReadingCSVHeader, err)
 	}
 
+	if len(header) == 1 {
+		return nil, nil, fmt.Errorf("%w: invalid separator detected, expected semicolon (;)", ErrCannotParseFile)
+	}
+
 	var meteoDataList []MeteoData
 	var rejectedDataList []RejectedMeteoData