Echo: Basic TCP echo server

Change-Id: I46e1f0e4d2733d14609efa68953e09b631cc28fb
diff --git a/apps/echo/go.mod b/apps/echo/go.mod
new file mode 100644
index 0000000..b958ea0
--- /dev/null
+++ b/apps/echo/go.mod
@@ -0,0 +1,3 @@
+module echo
+
+go 1.23.1