log/field.go
func Int64(key string, val int64) Field {
	return Field{
		key:        key,
		fieldType:  int64Type,
		numericVal: val,
	}
}
func Int64(key string, val int64) Field {
	return Field{
		key:        key,
		fieldType:  int64Type,
		numericVal: val,
	}
}
func Int64 ( key string , val int64 ) Field { return Field { key : key , fieldType : int64Type , numericVal : val , } }
// Int64 adds an int64-valued key:value pair to a Span.LogFields() record
Int64 adds an int64 - valued key : value pair to a Span . LogFields () record