fix: retaina and restore terminal mode on Windows (fixes #4251)

cmd/cleanup_other.go

@@ -0,0 +1,6 @@
+//go:build !windows
+// +build !windows
+
+package caddycmd
+
+func cleanup() error { return nil }

cmd/cleanup_windows.go

@@ -0,0 +1,24 @@
+//go:build windows
+// +build windows
+
+package caddycmd
+
+import "golang.org/x/sys/windows"
+
+// Retain the original mode of the console to restore later.
+// See: https://github.com/caddyserver/caddy/issues/4251
+// The evaluation of this takes place before calling init()
+// ref: https://golang.org/ref/spec#Order_of_evaluation
+var inMode, outMode uint32
+var _ = windows.GetConsoleMode(windows.Stdin, &inMode)
+var _ = windows.GetConsoleMode(windows.Stdout, &outMode)
+
+func cleanup() error {
+	if err := windows.SetConsoleMode(windows.Stdin, inMode); err != nil {
+		return err
+	}
+	if err := windows.SetConsoleMode(windows.Stdout, outMode); err != nil {
+		return err
+	}
+	return nil
+}

cmd/main.go

@@ -85,7 +85,9 @@ func Main() {
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "%s: %v\n", subcommand.Name, err)
 	}
-
+	if err := cleanup(); err != nil {
+		fmt.Fprintf(os.Stderr, "error restoring console to functional state: %v\n", err)
+	}
 	os.Exit(exitCode)
 }
 

go.mod

@@ -27,6 +27,7 @@ require (
 	go.uber.org/zap v1.19.0
 	golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e
 	golang.org/x/net v0.0.0-20210614182718-04defd469f4e
+	golang.org/x/sys v0.0.0-20210630005230-0f9fa26af87c
 	golang.org/x/term v0.0.0-20210503060354-a79de5458b56
 	google.golang.org/genproto v0.0.0-20210604141403-392c879c8b08
 	google.golang.org/protobuf v1.27.1