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"
+}

go.mod

@@ -4,6 +4,7 @@ require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/konsorten/go-windows-terminal-sequences v0.0.0-20180402223658-b729f2633dfe
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/stretchr/objx v0.1.1 // indirect
 	github.com/stretchr/testify v1.2.2
 	golang.org/x/crypto v0.0.0-20180904163835-0709b304e793
 	golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33

go.sum

@@ -4,6 +4,8 @@ github.com/konsorten/go-windows-terminal-sequences v0.0.0-20180402223658-b729f26
 github.com/konsorten/go-windows-terminal-sequences v0.0.0-20180402223658-b729f2633dfe/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.1 h1:2vfRuCMp5sSVIDSqO8oNnWJq7mPa6KVP3iPIwFBuy8A=
+github.com/stretchr/objx v0.1.1/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 golang.org/x/crypto v0.0.0-20180904163835-0709b304e793 h1:u+LnwYTOOW7Ukr/fppxEb1Nwz0AtPflrblfvUudpo+I=