bug fix and example added

examples/set_sessions.py

@@ -0,0 +1,19 @@
+# -*- encoding: utf-8 -*-
+
+from sanic import Sanic
+from sanic.response import json
+
+app = Sanic()
+
+
+@app.route("/")
+async def test(request):
+    if request.session.get('key') is None:
+        request.session['key'] = 'value'
+        return json(dict(ok=True))
+    else:
+        return json(dict(key=request.session['key']))
+
+
+if __name__ == "__main__":
+    app.run(host="0.0.0.0", port=8000)