Got rid of IsTerminal call to reduce external dependencies

terminal_check_aix.go

@@ -1,9 +1,9 @@
-// +build !appengine,!js,!windows,aix
+// +build aix
 
 package logrus
 
-import "io"
+import (
+	"golang.org/x/sys/unix"
+)
 
-func checkIfTerminal(w io.Writer) bool {
-	return false
-}
+const ioctlReadTermios = unix.TCGETS

terminal_check_bsd.go

@@ -0,0 +1,7 @@
+// +build darwin dragonfly freebsd netbsd openbsd
+
+package logrus
+
+import "golang.org/x/sys/unix"
+
+const ioctlReadTermios = unix.TIOCGETA

terminal_check_linux.go

@@ -0,0 +1,7 @@
+// +build linux
+
+package logrus
+
+import "golang.org/x/sys/unix"
+
+const ioctlReadTermios = unix.TCGETS

terminal_check_notappengine.go

@@ -1,4 +1,4 @@
-// +build !appengine,!js,!windows,!aix
+// +build !appengine,!js,!windows
 
 package logrus
 
@@ -6,13 +6,15 @@ import (
 	"io"
 	"os"
 
-	"golang.org/x/crypto/ssh/terminal"
+	"golang.org/x/sys/unix"
 )
 
 func checkIfTerminal(w io.Writer) bool {
 	switch v := w.(type) {
 	case *os.File:
-		return terminal.IsTerminal(int(v.Fd()))
+		_, err := unix.IoctlGetTermios(int(v.Fd()), ioctlReadTermios)
+
+		return err == nil
 	default:
 		return false
 	}