rewrite checkpoint

vendor/gopkg.in/op/go-logging.v1/example_test.go

@@ -0,0 +1,40 @@
+package logging
+
+import "os"
+
+func Example() {
+	// This call is for testing purposes and will set the time to unix epoch.
+	InitForTesting(DEBUG)
+
+	var log = MustGetLogger("example")
+
+	// For demo purposes, create two backend for os.Stdout.
+	//
+	// os.Stderr should most likely be used in the real world but then the
+	// "Output:" check in this example would not work.
+	backend1 := NewLogBackend(os.Stdout, "", 0)
+	backend2 := NewLogBackend(os.Stdout, "", 0)
+
+	// For messages written to backend2 we want to add some additional
+	// information to the output, including the used log level and the name of
+	// the function.
+	var format = MustStringFormatter(
+		`%{time:15:04:05.000} %{shortfunc} %{level:.1s} %{message}`,
+	)
+	backend2Formatter := NewBackendFormatter(backend2, format)
+
+	// Only errors and more severe messages should be sent to backend2
+	backend2Leveled := AddModuleLevel(backend2Formatter)
+	backend2Leveled.SetLevel(ERROR, "")
+
+	// Set the backends to be used and the default level.
+	SetBackend(backend1, backend2Leveled)
+
+	log.Debugf("debug %s", "arg")
+	log.Error("error")
+
+	// Output:
+	// debug arg
+	// error
+	// 00:00:00.000 Example E error
+}