go - graphql-go 标量返回类型的联合

Question

我正在尝试创建一个文件，该文件将是字符串、日期或 int

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
        },
    },
})

我试过，graphql.NewUnion但它似乎不接受标量类型