Priority on Select cases with channel

I have this function so that the methods inside, run on a ticker. My problem is that the second case, sigC, only works after the case ticker.C is complete, which is not ideal because the program runs with flags, so if I want to change the flags and alter the program's behaviour, I have to wait for the ticker methods to finish running, and that can take some time.

My objective is that when I press Ctrl+C, the program finishes running immediately.

func report() error {
	ticker := time.NewTicker(timeConfig)

	sigC := make(chan os.Signal, 1)
	signal.Notify(sigC, syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT, os.Interrupt)

	for range ticker.C {
		select {
		case <-ticker.C:
			connection = connectionInit()

			tagValues, err := fetchLatestTags()
			if err != nil {
				return err
			}
			if len(tagValues) >= threshold {
				metrics, err := fetchMetrics(tagValues)
				if err != nil {
					return err
				}
				if stdout {
					err = locally(metrics)
					if err != nil {
						return err
					}
				} else {
					err = sendMail(metrics)
					if err != nil {
						return err
					}
				}
			}
			connection.Close()
		case <-sigC:
			return nil
		}
	}
	return nil
}

I tried these solutions which are pretty similar to each other but to no avail:

[1]https://stackoverflow.com/questions/46200343/force-priority-of-go-select-statement

[2]https://stackoverflow.com/questions/11117382/priority-in-go-select-statement-workaround

If I understood correctly what you want to do is to replace the range-over-channel loop with an infinite loop. i.e. for range ticker.C { ... } -> for { ... }.

And if you want the program, rather than the report function, to finish immediately without waiting on the code in the case <-ticker.C: block to finish, you should execute that block of code in a separate goroutine and update the case <-sigC: block from return nil to os.Exit(1).

func report() {
	ticker := time.NewTicker(timeConfig)
	defer ticker.Stop()

	sigC := make(chan os.Signal, 1)
	signal.Notify(sigC, syscall.SIGHUP, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT, os.Interrupt)

	for {
		select {
		case <-ticker.C:
			go func() {
				connection = connectionInit()

				tagValues, err := fetchLatestTags()
				if err != nil {
					return
				}
				if len(tagValues) >= threshold {
					metrics, err := fetchMetrics(tagValues)
					if err != nil {
						return
					}
					if stdout {
						err = locally(metrics)
						if err != nil {
							return
						}
					} else {
						err = sendMail(metrics)
						if err != nil {
							return
						}
					}
				}
				connection.Close()
			}()
		case <-sigC:
			os.Exit(1)
		}
	}
}