How Can I Define Multiple Name Tags for Fields in a Go Struct?

Multiple Name Tags in a Go Struct

When working with structs in Go, it can be useful to define multiple name tags to represent the same field in different contexts. This is especially useful when dealing with third-party libraries or APIs that expect data in a specific format.

Issue: Defining Multiple Name Tags in a Struct

Consider the following example:

type Page struct {
    PageId string                 `bson:"pageId"`
    Meta   map[string]interface{} `bson:"meta"`
}

This struct is designed to represent a Mongo database document, with the PageId field tagged for MongoDB (bson) and the Meta field tagged for MongoDB as well. However, when encoding this struct to JSON, the PageId field is rendered as PageId (in uppercase) instead of pageId.

Solution: Using Space as Tag Separator

To define multiple name tags for a field, use space instead of commas as the separator between tags. Here's an updated version of the struct:

type Page struct {
    PageId string                 `bson:"pageId" json:"pageId"`
    Meta   map[string]interface{} `bson:"meta" json:"meta"`
}

With this modification, the PageId field is tagged for both MongoDB (as pageId) and JSON (as pageId). This ensures that the field will be named appropriately when interacting with MongoDB or encoding to JSON.

Documentation Reference

The Go reflect package documentation specifies the convention for tag strings:

By convention, tag strings are a concatenation of optionally space-separated key:"value" pairs.

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