How to achieve concurrent Transactions works with DB

[Rohik_Galli]

I want to create a secure payment service where user may deposit funds, withdraw funds, and there may be transacions between two accounts.
I want to achieve transactions works concurrently.I am using postgreSQL as a DB.
Please help me out how can I create this ?

[Akezhan_Esbolatov]

As far as I know, access to the database shouldn’t be concurrent, because your one gorutine may change the state of database while another gorutine is trying to read some data from the database