The basic idea is to just have the function send to one student at a time and then have a utility function that does a for loop and calls the sendStudentEmail() function for each upon adding all students to a class. I think you'll find it more intuitive.

```go
func addStudentHandler(w, r) {
    ... //get students from db
    go sendStudentEmail()
}

func sendStudentEmail(cid, email, name string) {
       //get students map from db for cid... could be redundant but premature optimization yada yada ...
     
	num := make([]byte, 32)
	_, err = rand.Read(num)

       studId, err := base64.encode(num) //just have to look up how to use this lib
       // rationale: base64 will give a human readable output of the previously made random []byte
       // you'll have to mess with the lengths in order to get something reasonable (e.g. 20 chars)

      //send email (what you have below looks great, just add cid and id to the body).

      students = append(students, map[string]interface{}{"name":name, "email": email, "id": studId)
      //update class in db at cid with new added student.
}

//so then addClass works more like: 
func addClassHandler(w, r) {
   // get json of students from request body

   // you could put this is a func, whatever you're feeling
   for _, s := range students { 
       go sendStudentEmail(cid, s["name"], s["email"])
   }
}
````

Don't let this detract from the fact that I think this is a nice change. Code reviews are not personal nor negative. I just want to offer suggestions and pointers.