Closer 
The aim of this package is to provide an universal way to catch the event of application’s exit and perform some actions before it’s too late. closer doesn’t care about the way application tries to exit, i.e. was that a panic or just a signal from the OS, it calls the provided methods for cleanup and that’s the whole point.
Usage
Be careful, this package is using the singleton pattern (like net/http does) and doesn't require any initialisation step. However, there’s an option to provide a custom configuration struct.
// Init allows user to override the defaults (a set of OS signals to watch for, for example).
func Init(cfg Config)
// Close sends a close request.
// The app will be terminated by OS as soon as the first close request will be handled by closer, this
// function will return no sooner. The exit code will always be 0 (success).
func Close()
// Bind will register the cleanup function that will be called when closer will get a close request.
// All the callbacks will be called in the reverse order they were bound, that's similar to how `defer` works.
func Bind(cleanup func())
// Checked runs the target function and checks for panics and errors it may yield. In case of panic or error, closer
// will terminate the app with an error code, but either case it will call all the bound callbacks beforehand.
// One can use this instead of `defer` if you need to care about errors and panics that always may happen.
// This function optionally can emit log messages via standard `log` package.
func Checked(target func() error, logging bool)
// Hold is a helper that may be used to hold the main from returning,
// until the closer will do a proper exit via `os.Exit`.
func Hold()The the usage examples: example, example-error and example-panic.
Table of exit codes
All errors and panics will be logged if the logging option of closer.Checked was set true, also the exit code (for os.Exit) will be determined accordingly:
| Event | Default exit code |
|---|---|
| error = nil | 0 (success) |
| error != nil | 1 (failure) |
| panic | 1 (failure) |