Wrap context flow inside a run func

[agiacomolli]

These contexts are not handled correctly because of os.Exit():

go-inter/cmd/inter-banking/main.go

Lines 60 to 61 in fcc3e16

	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt)
	defer cancel()

go-inter/cmd/inter-token/main.go

Lines 52 to 53 in fcc3e16

	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt)
	defer cancel()

As per docs:

... The program terminates immediately; deferred functions are not run.

Better to wrap the flow inside a run that returns an error:

func main() {
    err := run()
    if err != nil {
        fmt.Println(err)
        os.Exit(1)
    }
}

func run() error {
    ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt)
    defer cancel()

    ...

    return nil
}