Get json field in body request using Lua in NGINX

nginx-lua-get-token-body-json.conf

server {
    listen       80;
    server_name  localhost;

    location / {
        default_type application/json;
        access_by_lua_block  {
            ngx.req.read_body()
            local cjson = require "cjson"
            local body = cjson.decode(ngx.req.get_body_data())
            ngx.req.set_header("x-body-token", body.token)
        }

        proxy_read_timeout 300;
        proxy_pass https://postman-echo.com/post;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection keep-alive;
        proxy_set_header Host $host;
        proxy_cache_bypass $http_upgrade;
    }
}