Add DialWithDebugOutput to log commands.

debug.go

@@ -0,0 +1,21 @@
+package ftp
+
+import "io"
+
+type debugWrapper struct {
+	conn io.ReadWriteCloser
+	io.Reader
+	io.Writer
+}
+
+func newDebugWrapper(conn io.ReadWriteCloser, w io.Writer) io.ReadWriteCloser {
+	return &debugWrapper{
+		Reader: io.TeeReader(conn, w),
+		Writer: io.MultiWriter(w, conn),
+		conn:   conn,
+	}
+}
+
+func (w *debugWrapper) Close() error {
+	return w.conn.Close()
+}