1  
 2  program test.alpha {
 3      struct TokenInfo {
 4          id: u64,
 5      }
 6      mapping token_name_to_info: field => TokenInfo;
 7  
 8  
 9      async transition add_new_token_2() -> Future {
10          return finalize_add_new_token_2();
11      }
12  
13  
14      async function finalize_add_new_token_2() {
15          let try_get_token: TokenInfo = Mapping::get_or_use(
16              token_name_to_info,
17              0field,
18              TokenInfo { id: 0u64 }
19  	    );
20          if try_get_token.id == 0u64 {
21              try_get_token = TokenInfo { id: 10u64 };
22          } else {
23              return;
24          }
25      }
26  }
27  
28  
29