How to send RTMP url's query part to RTMP server

I try to hand write a RTMP publish / play client. The streaming server I used now is nginx with rtmp module.

My code follows the RTMP client's workflow, that something like Handshake -> Connect -> CreateStream -> Publish or Play.

It can work well when dealing simple RTMP url such as rtmp://127.0.0.1:1935/mylv/afv

But when verifying is needed, RTMP url will be rtmp://127.0.0.1:1935/mylv/afv?username=abc&password=123

rtmp {
     server {
        listen 1935;
        chunk_size 4000;
        application mylv { 
            live on;
            hls on;
            hls_path /mnt/datadisk0/uploadfile/live;
            allow play all;
            on_publish http://127.0.0.1:10078/user/auth; 
        }
    }
}

/// auth.py
from flask import Flask, request, Response
app = Flask(__name__)

@app.route('/user/auth',methods=['POST'])
def auth():
    user = request.form['username']
    password = request.form['password']
    print(user,'\t',password)

    auth_user ='abc'
    auth_passWord ='123'
    if auth_user == user and auth_passWord == password:
        return Response(response='success', status=200)
    else:
        return Response(status=500)
        #Flask.abort(404)
    return password


if __name__ == '__main__':
    app.run(host='0.0.0.0', port=10078, debug=True)

How I should do to send the query part username=abc&password=123 to server?