When generate model using goctl, the numeric type is treated as a bigint

[smokecat]

Describe the bug
A field of type numeric in the PostgreSQL database is generated as int64. And the numeric database type is treated as a bigint type in goctl.yaml

To Reproduce

1. The sql is

   create table demo (
     id bigint generated always as identity primary key,
     max_position decimal(20, 4) not null
   );

2. The genereated model struct is

   Demo struct {
     Id               int64          `db:"id"`
     MaxPosition      int64          `db:"max_position"`
   }

3. The goctl.yaml is

   model:
     types_map:
        bigint:
          null_type: sql.NullInt64
          type: int64
          unsigned_type: uint64
        decimal:
          null_type: decimal.NullDecimal
          pkg: github.com/shopspring/decimal
          type: decimal.Decimal

Expected behavior
The type of MaxPosition is decimal.Decimal

Environments (please complete the following information):

• go-zero version 1.7.2
• goctl version 1.7.2