Script to upload a file to Drive, request it be converted to spreadsheet, then export it as CSV

drive.go

package main

import (
	"encoding/json"
	"flag"
	"io"
	"log"
	"net/http"
	"os"
	"strings"
)

var (
	file  = flag.String("file", "", "file to convert")
	token = flag.String("token", "", "access token authorized to Drive API")
)

// RoundTripper that adds a token before making the request.
type tokenRT struct{}

func (t tokenRT) RoundTrip(r *http.Request) (*http.Response, error) {
	r.Header.Set("Authorization", "Bearer "+*token)
	c := http.Client{}
	return c.Do(r)
}

func main() {
	flag.Parse()
	f, err := os.Open(*file)
	if err != nil {
		log.Fatalf("%v", err)
	}
	defer f.Close()

	c := http.Client{
		Transport: tokenRT{},
	}

	// Upload file and request conversion
	iresp, err := c.Post("https://www.googleapis.com/upload/drive/v2/files?uploadType=media&convert=true", "application/vnd.ms-excel", f)
	if err != nil {
		log.Fatalf("%v", err)
	}
	defer iresp.Body.Close()
	if iresp.StatusCode != http.StatusOK {
		io.Copy(os.Stderr, iresp.Body)
		log.Fatalf("Error %d", iresp.StatusCode)
	}

	// Get the link to export to CSV
	var insertResp struct {
		ID          string
		ExportLinks map[string]string
	}
	if err := json.NewDecoder(iresp.Body).Decode(&insertResp); err != nil {
		log.Fatalf("%v", err)
	}
	link := insertResp.ExportLinks["application/pdf"]
	if link == "" {
		log.Fatalf("couldn't get export link")
	}
	link = strings.Replace(link, "=pdf", "=csv", 1) + "&access_token=" + *token

	// Fetch export link
	eresp, err := http.Get(link)
	if err != nil {
		log.Fatalf("%v", err)
	}
	defer eresp.Body.Close()
	if eresp.StatusCode != http.StatusOK {
		io.Copy(os.Stderr, eresp.Body)
		log.Fatalf("Error %d", eresp.StatusCode)
	}
	io.Copy(os.Stdout, eresp.Body)

	// Trash temporary file uploaded for conversion
	if _, err := c.Post("https://www.googleapis.com/drive/v2/files/"+insertResp.ID+"/trash", "application/json", nil); err != nil {
		log.Printf("failed to trash: %v", err)
	}
}