TUN-528: Move cloudflared into a separate repo

vendor/github.com/rifflock/lfshook/README.md

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+# Local Filesystem Hook for Logrus
+
+[![GoDoc](https://godoc.org/github.com/rifflock/lfshook?status.svg)](http://godoc.org/github.com/rifflock/lfshook)
+
+Sometimes developers like to write directly to a file on the filesystem. This is a hook for [`logrus`](https://github.com/sirupsen/logrus) which designed to allow users to do that. The log levels are dynamic at instantiation of the hook, so it is capable of logging at some or all levels.
+
+## Example
+```go
+import (
+	"github.com/rifflock/lfshook"
+	"github.com/sirupsen/logrus"
+)
+
+var Log *logrus.Logger
+
+func NewLogger() *logrus.Logger {
+	if Log != nil {
+		return Log
+	}
+
+	pathMap := lfshook.PathMap{
+		logrus.InfoLevel:  "/var/log/info.log",
+		logrus.ErrorLevel: "/var/log/error.log",
+	}
+
+	Log = logrus.New()
+	Log.Hooks.Add(lfshook.NewHook(
+		pathMap,
+		&logrus.JSONFormatter{},
+	))
+	return Log
+}
+```
+
+### Formatters
+`lfshook` will strip colors from any `TextFormatter` type formatters when writing to local file, because the color codes don't look great in file.
+
+If no formatter is provided via `lfshook.NewHook`, a default text formatter will be used.
+
+### Log rotation
+In order to enable automatic log rotation it's possible to provide an io.Writer instead of the path string of a log file.
+In combination with packages like [go-file-rotatelogs](https://github.com/lestrrat/go-file-rotatelogs) log rotation can easily be achieved.
+
+```go
+package main
+
+import (
+	"github.com/lestrrat/go-file-rotatelogs"
+	"github.com/rifflock/lfshook"
+	"github.com/sirupsen/logrus"
+)
+
+var Log *logrus.Logger
+
+func NewLogger() *logrus.Logger {
+	if Log != nil {
+		return Log
+	}
+
+	path := "/var/log/go.log"
+	writer := rotatelogs.New(
+		path+".%Y%m%d%H%M",
+		rotatelogs.WithLinkName(path),
+		rotatelogs.WithMaxAge(time.Duration(86400)*time.Second),
+		rotatelogs.WithRotationTime(time.Duration(604800)*time.Second),
+	)
+
+	logrus.Hooks.Add(lfshook.NewHook(
+		lfshook.WriterMap{
+			logrus.InfoLevel:  writer,
+			logrus.ErrorLevel: writer,
+		},
+		&logrus.JSONFormatter,
+	))
+
+	Log = logrus.New()
+	Log.Hooks.Add(lfshook.NewHook(
+		pathMap,
+		&logrus.JSONFormatter{},
+	))
+
+	return Log
+}
+```
+
+### Note:
+User who run the go application must have read/write permissions to the selected log files. If the files do not exists yet, then user must have permission to the target directory.