log/field.go
func (lf Field) String() string {
	return fmt.Sprint(lf.key, ":", lf.Value())
}
func (lf Field) String() string {
	return fmt.Sprint(lf.key, ":", lf.Value())
}
func ( lf Field ) String ( ) string { return fmt . Sprint ( lf . key , " " , lf . Value ( ) ) }
// String returns a string representation of the key and value.
String returns a string representation of the key and value .