type User struct {
	gorm.Model
	Name      string `gorm:"uniqueIndex;size:255"`
}

2023/02/04 17:37:52 /home/runner/go/pkg/mod/gorm.io/driver/postgres@v1.4.6/migrator.go:339 ERROR: relation "idx_users_name" already exists (SQLSTATE 42P07)
[0.881ms] [rows:0] ALTER TABLE "users" ADD CONSTRAINT "idx_users_name" UNIQUE("name")
    main_test.go:18: Failed, migrate error: ERROR: relation "idx_users_name" already exists (SQLSTATE 42P07)