log/field.go
func String(key, val string) Field {
	return Field{
		key:       key,
		fieldType: stringType,
		stringVal: val,
	}
}
func String(key, val string) Field {
	return Field{
		key:       key,
		fieldType: stringType,
		stringVal: val,
	}
}
func String ( key , val string ) Field { return Field { key : key , fieldType : stringType , stringVal : val , } }
// String adds a string-valued key:value pair to a Span.LogFields() record
String adds a string - valued key : value pair to a Span . LogFields () record