An executable Go program starts at main() in package main. The package declaration tells the compiler to produce a standalone program; it then looks for main() among the files in that package. With both present, the result is an executable that can run from the command line. section 2.4.5
Keep each executable’s entry point in its own main package. A project with several tools or services can place them in separate subdirectories under cmd, such as cmd/myapp/main.go, while sharing code through other packages. section 11.1.1
Starting work is not the same as finishing it
An RSS reader can fetch a feed inside main(). Moving the fetch into a goroutine lets main() continue, but if main() returns immediately, the program exits before the feed title is printed. main() must remain active until background work finishes; a fixed sleep only guesses at the required time. section 9.1
Listing 9.3 main.go: Fetching data via a goroutine
package main
...
func main() {
fp := gofeed.NewParser()
go func(url string) { #1
feed, _ := fp.ParseURL(url) #2
fmt.Println(feed.Title)
}("https://rss.nytimes.com/services/xml/rss/nyt/World.xml") #3
}
The asynchronous RSS-fetch listing shows main() launching a goroutine with no subsequent wait, exposing why the entry point also governs program lifetime. section 9.1
