code: func formatWithFields(format string, fields logging.Fields, args []interface{}) string {
  	fieldString := fields.String()
  
  	buf := bytes.Buffer{}
  	buf.Grow(len(format) + logMessageFieldPadding + len(fieldString))
  	fmt.Fprintf(&buf, format, args...)
  
  	padding := 44 - buf.Len()
  	if padding < 1 {
  		padding = 1
  	}
  	for i := 0; i < padding; i++ {
  		buf.WriteString(" ")
  	}
  	buf.WriteString(fieldString)
  	return buf.String()
  }
docs: // formatWithFields renders the supplied format string, adding fields.