add logout api

route/api/index.js

@@ -55,6 +55,11 @@ r.post('/login', koaBody(), async (c, n) => {
   c.obj = resObject('Success')
 })
 
+r.post('/logout', async (c, n) => {
+  c.session = null
+  c.obj = resObject('Success')
+})
+
 r.get('/session', checkSession, async (c, n) => {
   c.obj = resObject('Success', {
     user: c.state.loginUser