How do I do the same for multiple conflicts in PostgreSQL?

For example, if I have a table:

create table test(

    username                varchar(50)   PRIMARY KEY,      
    customer                varchar(12),
    nickname                varchar(12)  
);

create unique index unique_customer_nickname on test(customer,nickname);

      

        
        
        
      

    

Therefore, the username is unique and (client, alias) together are unique.

Then if I want to write an upsert statement like this:

Insert into test(username,customer,nickname) values('utest','ctest','ntest') 
on conflict(username) or on conflict(customer,nickname) DO UPDATE ....

      

        
        
        
      

    

but that gives me a syntax error. I also tried on (conflict(username) or conflict(customer,nickname))

but this also returns a syntax error.

so I want different conflicts to do the same thing.