Improved documentation of Fatal Handlers

README.md

@@ -384,3 +384,19 @@ assert.Equal("Hello error", hook.LastEntry().Message)
 hook.Reset()
 assert.Nil(hook.LastEntry())
 ```
+
+#### Fatal handlers
+
+Logrus can register one or more functions that will be called when any `fatal`
+level message is logged. The registered handlers will be executed before
+logrus performs a `os.Exit(1)`. This behavior may be helpful if callers need
+to gracefully shutdown. Unlike a `panic("Something went wrong...")` call which can be intercepted with a deferred `recover` a call to `os.Exit(1)` can not be intercepted.
+
+```
+...
+handler := func() {
+  // gracefully shutdown something...
+}
+logrus.RegisterExitHandler(handler)
+...
+```

alt_exit.go

@@ -51,9 +51,14 @@ func Exit(code int) {
 	os.Exit(code)
 }
 
-// RegisterExitHandler adds a Logrus atexit handler, call logrus.Exit to invoke
+// RegisterExitHandler adds a Logrus Exit handler, call logrus.Exit to invoke
 // all handlers. The handlers will also be invoked when any Fatal log entry is
 // made.
+//
+// This method is useful when a caller wishes to use logrus to log a fatal
+// message but also needs to gracefully shutdown. An example usecase could be
+// closing database connections, or sending a alert that the application is
+// closing.
 func RegisterExitHandler(handler func()) {
 	handlers = append(handlers, handler)
 }