Given the following function:
func main() {
l := createListener(8080)
r := ksws.CreateRouter()
if err := http.Serve(l, r); err != nil {
fmt.Println("An error occured.")
}
}
I'm wondering why I should catch the 'error' returned from the 'http.Serve' method? It seems that an error is never returned here.
However, according to the documentation https://golang.org/pkg/net/http/#Serve the Serve method always returns a non-nill error.
Can someone provide me some guidance on this?
Simple case: when port 8080 already used you'll have error:
listen tcp :8080: bind: address already in use
Another case: http.Serve calls srv.trackListener which also may fail in case go didn't manage to add listener.
Also: http.Serve calls l.Accept() which also may fail...
So there are many possible cases...
And also it's idiomatic for go to check all errors returned by any function.
PS: It's way better to have redundant error check than to have silent not working program (imho)...
Take a look at the source code and it might shine some light into your question.
https://golang.org/src/net/http/server.go?s=75585:75634#L2838
// Serve always returns a non-nil error and closes l. // After Shutdown or Close, the returned error is ErrServerClosed.
So the error will alway be return either with a real error if something went wrong or the ErrServerClosed in case of a shutdown or close, which happen for several reasons.
in your code when you ctrl-c, note that the prints does not occur because the program has ended. you should listen to signals to prevent that behavior.
package main
import (
"fmt"
"net/http"
"os"
"os/signal"
"time"
)
func main() {
c := make(chan os.Signal, 1)
signal.Notify(c, os.Interrupt)
r := http.NewServeMux()
srv := &http.Server{
Addr: ":0",
Handler: r,
}
go func() {
if err := srv.ListenAndServe(); err != nil {
fmt.Println("An error occured.")
}
}()
// Block until a signal is received.
<-c
srv.Close()
fmt.Println("rr")
<-time.After(time.Second)
}