graphql-标量联合返回类型

Question

我正在尝试创建一个将是字符串，日期或整数的文件

var PredSearchElementType = graphql.NewObject(graphql.ObjectConfig{
    Name: "PredSearchElementType",
    Fields: graphql.Fields{
        "_id": &graphql.Field{
            Type: ObjectID,
        },
        "field_name": &graphql.Field{
            Type: graphql.String,
        },
        "field_criteria": &graphql.Field{
            Type: graphql.String,
        },
        "field_value": &graphql.Field{
            Type: graphql.String,// this field can be a string or a date or an int
        },
    },
})

我尝试过graphql.NewUnion，但它似乎不接受标量类型