Added terminal check on Windows

terminal_check_notappengine.go

@@ -1,4 +1,4 @@
-// +build !appengine,!gopherjs
+// +build !appengine,!gopherjs,!windows
 
 package logrus
 

terminal_check_windows.go

@@ -0,0 +1,20 @@
+// +build !appengine,!gopherjs,windows
+
+package logrus
+
+import (
+	"io"
+	"os"
+	"syscall"
+)
+
+func checkIfTerminal(w io.Writer) bool {
+	switch v := w.(type) {
+	case *os.File:
+		var mode uint32
+		err := syscall.GetConsoleMode(syscall.Handle(v.Fd()), &mode)
+		return err == nil
+	default:
+		return false
+	}
+}