A Go Package for Fetching Feeds

I have been looking into various things to create a simple bot, inspired by "[Introduction to Creating Twitter Bots with Shell Scripts](https://zenn.dev/mattn/books/bb181f3f4731920f29a5 "シェルスクリプトで作る Twitter bot 作成入門 | Zenn")"^[1]. While searching for a Go package with a simple structure to retrieve RSS/Atom feeds published by blogs and other sites, I found a perfect one.

• mmcdole/gofeed: Parse RSS, Atom and JSON feeds in Go

What makes mmcdole/gofeed excellent is that it consumes feeds regardless of their type and maps them into a unified structure. For example, it looks like this:

sample.go

package main

import (
    "fmt"
    "os"
    "time"

    "github.com/mmcdole/gofeed"
)

func main() {
    feed, err := gofeed.NewParser().ParseURL("https://zenn.dev/spiegel/feed")
    if err != nil {
        fmt.Fprintln(os.Stderr, err)
        return
    }
    fmt.Println(feed.Title)
    fmt.Println(feed.FeedType, feed.FeedVersion)
    for _, item := range feed.Items {
        if item == nil {
            break
        }
        fmt.Println(item.Title)
        fmt.Println("\t-2", item.Link)
        fmt.Println("\t-2", item.PublishedParsed.Format(time.RFC3339))
    }
}

The execution result of this code looks like this:

$ go run sample.go 
Spiegel's feed
rss 2.0
Running a full suite of CI tasks for Go packages with GitHub Actions
        -> https://zenn.dev/spiegel/articles/20200929-using-golangci-lint-action
        -> 2020-09-29T10:27:34Z
errors.Is and errors.As are not (just) comparison functions
        -> https://zenn.dev/spiegel/articles/20200926-error-handling-with-golang
        -> 2020-09-26T06:54:49Z
...

It also supports the standard context package, so you can write it with cancellation events, for example, under concurrent processing (goroutine) like this:

ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
defer cancel()
feed, err := gofeed.NewParser().ParseURLWithContext("https://zenn.dev/spiegel/feed", ctx)
if err != nil {
    return
}
...

All right. This looks useful.

References

https://text.baldanders.info/golang/ticker/

脚注

1. I've been using IFTTT to feed blog update information to Twitter, but even though I barely use it, they've been [persistently telling me to upgrade and pay](https://forest.watch.impress.co.jp/docs/news/1278901.html "無償版“IFTTT”で利用可能なアプレットは3つまでに ～超過分は10月8日にアーカイブ - 窓の杜"). They send emails almost every day. I'm not interested in spammy services.