concurrent-booking

System design reading is boring, let's build

1. create data base.
2. add mock data
3. can use setup.sql
4. add version in table.
5. go run main.go concurrency_control.go
6. use api
   1. for booking with different method.
   2. find the status of existing.
   3. do payment.
   4. cache removal or time out for seat is 1 min, after that if not able to pay then seat will be available for others.