log/field.go
func Object(key string, obj interface{}) Field {
	return Field{
		key:          key,
		fieldType:    objectType,
		interfaceVal: obj,
	}
}
func Object(key string, obj interface{}) Field {
	return Field{
		key:          key,
		fieldType:    objectType,
		interfaceVal: obj,
	}
}
// Object adds an object-valued key:value pair to a Span.LogFields() record