services.AddScoped<IUserRepository, UserRepository>();
services.AddScoped<IXRepository, XRepository>();
... 40 more lines ...

// IRepository.cs
public interface IRepository
{
}

// IUserRepository.cs
public interface IUserRepository : IRepository
{
    User ReadToken(string email, string password);
}

// BaseRepository.cs
public class BaseRepository : IDisposable
{
    protected IDbConnection PostgreSQL;

    public BaseRepository(IDbConnection postgreSQL)
    {
        PostgreSQL = postgreSQL;
    }

    public void Dispose()
    {
    }
}

// UserRepository.cs
public class UserRepository : BaseRepository, IUserRepository
{
    public UserRepository(IDbConnection postgreSQL) : base(postgreSQL)
    {
    }

    public User ReadToken(string email, string password)
    {
        object parameters;
        string sql;

        parameters = new
        {
            email,
            password
        };

        sql =
        @"
        SELECT
            user_id AS id,
            token
        FROM users
        WHERE
            email = @email AND
            password = CRYPT(@password, senha) AND
            active = TRUE;
        ";

        var user = base.PostgreSQL.Query<User>(sql, parameters).SingleOrDefault();

        if (user == null)
            throw new UnauthorizedException("User", "User not found.");

        return user;
    }
}

// UsersController.cs
public class UsersController : ControllerBase
{
    protected IUserRepository UserRepository;

    public UsersController(IUserRepository userRepository)
    {
        UserRepository = userRepository;
    }
}

// Startup.cs
services.AddScoped<IRepository, BaseRepository>();