Strange type definition syntax in Golang (name, then type, then string literal)

Question

I\'ve been trying to find out how to use mgo (MongoDB driver for Go) and I came across this struct declaration:

type Something struct {
    Id bson.ObjectId          


        

Answer 1

It's explained in the Struct types section of the language specification:

A field declaration may be followed by an optional string literal tag, which becomes an attribute for all the fields in the corresponding field declaration. The tags are made visible through a reflection interface but are otherwise ignored.

// A struct corresponding to the TimeStamp protocol buffer.
// The tag strings define the protocol buffer field numbers.
struct {
    microsec  uint64 "field 1"
    serverIP6 uint64 "field 2"
    process   string "field 3"
}