Example of calling the Google's Merchant API (content scope) from Go lang.

products.go

// Package products is an example of calling the Google's Merchant API (content scope) from Go lang.
package products

import (
	"strconv"

	"code.google.com/p/goauth2/oauth"
	"code.google.com/p/google-api-go-client/content/v2"
)

// Product represents a Google Merchant product.
type Product struct {
	ID          string
	Name        string
	ImageURL    string
	LocationURL string
	Price       float32
	Currency    string
	Type        string
}

// Fetcher stores the state and keys.
type Fetcher struct {
	config    *oauth.Config
	transport *oauth.Transport
	svc       *content.Service
}

// Config represents the credentials used for OAuth2 authorization.
type Config struct {
	AccessToken  string
	ClientId     string
	ClientSecret string
}

// NewFetcher returns a new fetcher supplied with credentials.
func NewFetcher(cfg *Config) (f *Fetcher, err error) {
	f = &Fetcher{}
	f.config = &oauth.Config{
		ClientId:     cfg.ClientId,
		ClientSecret: cfg.ClientSecret,
		Scope:        content.ContentScope,
		AuthURL:      "https://accounts.google.com/o/oauth2/auth",
		TokenURL:     "https://accounts.google.com/o/oauth2/token",
	}
	f.transport = &oauth.Transport{
		Config: f.config,
		Token:  &oauth.Token{AccessToken: cfg.AccessToken},
	}
	f.svc, err = content.New(f.transport.Client())
	return
}

// Fetch fetches all products from the given merchant's account. You should create a
// productChan with sufficient size, otherwise this method will block.
func (f *Fetcher) Fetch(merchantId uint64, productChan chan<- *Product) (err error) {
	var list *content.ProductsListResponse
	if list, err = f.svc.Products.List(merchantId).Do(); err != nil {
		return
	}
	for _, res := range list.Resources {
		p := &Product{}
		p.ID = res.Id
		p.ImageURL = res.ImageLink
		p.LocationURL = res.Link
		p.Name = res.Title
		p.Currency = res.Price.Currency
		p.Type = "photo"
		var price float64
		if price, err = strconv.ParseFloat(res.Price.Value, 32); err != nil {
			return
		}
		p.Price = float32(price)
		productChan <- p
	}
	return
}