Add an example for tracing global variable with hook

example_global_hook_test.go

@@ -0,0 +1,37 @@
+package logrus_test
+
+import (
+	"github.com/sirupsen/logrus"
+	"os"
+)
+
+var (
+	mystring string
+)
+
+type GlobalHook struct {
+}
+
+func (h *GlobalHook) Levels() []logrus.Level {
+	return logrus.AllLevels
+}
+
+func (h *GlobalHook) Fire(e *logrus.Entry) error {
+	e.Data["mystring"] = mystring
+	return nil
+}
+
+func Example() {
+	l := logrus.New()
+	l.Out = os.Stdout
+	l.Formatter = &logrus.TextFormatter{DisableTimestamp: true}
+	l.Formatter.(*logrus.TextFormatter).DisableTimestamp = true
+	l.AddHook(&GlobalHook{})
+	mystring = "first value"
+	l.Info("first log")
+	mystring = "another value"
+	l.Info("second log")
+	// Output:
+	// level=info msg="first log" mystring="first value"
+	// level=info msg="second log" mystring="another value"
+}