[FIX] api bug

src/api/group.js

@@ -33,7 +33,7 @@ export const getStudentGroup = (courseId = -1) => {
  */
 export const putStudentGroup = code => {
   return request(`${GROUP_MODULE}`, {
-    method: "POST",
+    method: "PUT",
     body: {
       code: code || null
     }