diff --git a/.gitignore b/.gitignore
index 142d860..0eea20a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,3 +6,4 @@ dist/
 MANIFEST
 
 \.vscode/
+env
\ No newline at end of file
diff --git a/postgres_kernel/kernel.py b/postgres_kernel/kernel.py
index 82d54da..95c15ef 100644
--- a/postgres_kernel/kernel.py
+++ b/postgres_kernel/kernel.py
@@ -15,7 +15,7 @@
 
 
 def log(val):
-    return # comment out line for debug
+    return  # comment out line for debug
     with open('kernel.log', 'a') as f:
         f.write(str(val) + '\n')
     return val
@@ -57,7 +57,8 @@ def __init__(self, **kwargs):
         self._conn_string = os.getenv('DATABASE_URL', '')
         self._autocommit = True
         self._conn = None
-        self._start_connection()
+        if self._conn_string:
+            self._start_connection()
 
     @property
     def language_version(self):
@@ -154,8 +155,10 @@ def change_autocommit_mode(self, switch):
 
     def do_execute(self, code, silent, store_history=True,
                    user_expressions=None, allow_stdin=False):
+        if code.strip() in ['quit', 'quit()', 'exit', 'exit()']:
+            # self.do_shutdown(True)
+            return {'status': 'ok', 'execution_count': self.execution_count, 'payload': [{"source": "ask_exit"}]}
         print(code)
-
         connection_string = self.CONN_STRING_COMMENT.findall(code)
         autocommit_switch = self.AUTOCOMMIT_SWITCH_COMMENT.findall(code)
         if autocommit_switch:
@@ -204,7 +207,7 @@ def do_execute(self, code, silent, store_history=True,
                     self.iopub_socket, 'stream', {
                         'name': 'stdout',
                         'text': str(notice)
-                })
+                    })
             self._conn.notices = []
 
             if header is not None and len(rows) > 0:
diff --git "a/\350\241\245\345\205\205\350\257\264\346\230\216.md" "b/\350\241\245\345\205\205\350\257\264\346\230\216.md"
new file mode 100644
index 0000000..4be52e9
--- /dev/null
+++ "b/\350\241\245\345\205\205\350\257\264\346\230\216.md"
@@ -0,0 +1,17 @@
+# 补充说明
+
+本项目为[bgschiller/postgres_kernel](https://github.com/bgschiller/postgres_kernel)的fork,解决了不先设置环境变量`DATABASE_URL`就无法使用的问题,以及jupyter console中无法通过quit或者exit退出的问题.
+
+本项目已经提交了pull-request,但介于原项目已经3年多没更新了估计也不会被merge了.需要使用jupyter连pg的朋友可以有两种途径
+
+1. 直接安装本项目
+    ```bash
+    pip install git+https://github.com/Basic-Components/postgres_kernel.git
+    ```
+2. 安装我的另一个项目[postgresql_kernel](https://github.com/Python-Tools/postgresql_kernel)
+
+    ```bash
+    pip install postgresql_kernel
+    ```
+
+    这个项目使用[metakernel](https://github.com/Calysto/metakernel)构造,目前已经完全实现了postgres_kernel的功能,而且用法一样.后续我则会进一步扩展这个kernel以实现一些自己的需求.
\ No newline at end of file