get("/getUser/:user",(request,response)-> {
        response.type("application/json");
        Account acc = gson.fromJson(request.params(":user"), Account.class);
        return getUser(acc);
    }, gson ::toJson);

private static Info getUser(Account acc) throws ClassNotFoundException, SQLException, UnsupportedEncodingException, NoSuchAlgorithmException {
    Connection c;
    Statement stm = null;
    Class.forName("org.postgresql.Driver");
    c = DriverManager.getConnection("jdbc:postgresql://<myIP>:5432/egecalc", "postgres", "itsMyAppBitches");
    String sql = "select * from users;";
    Info result = null;
    String hash = getHash(acc.getPassword());
    stm = c.createStatement();
    ResultSet rs = stm.executeQuery(sql);
    while (rs.next()) {
        if (rs.getString("username").equals(acc.getUsername())) {
            if (rs.getString("password").equals(acc.getPassword())) {
                result = new Info("successful");
                break;
            } else {
                result = new Info("invalid password");
                break;
            }
        }
        else
            result = new Info("invalid username");
    }
    rs.close();
    c.close();
    return result;
}

public interface getUser{
    @GET("/getUser/{user}")
    Call<Info> CurrUser(@Path("user") String str);
}

public class Info {
@SerializedName("information")
@Expose
private String information;

public Info(String information) {
    this.information = information;
}

public String getInformation() {
    return information;
}

public class AutirizationAPI {
private static String BASE_URL = "http://<myIP>:4567";
public static EgeCalcApi.getUser getApi() {
    Gson gson = new GsonBuilder()
            .setLenient()
            .create();
    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(BASE_URL)
            .addConverterFactory(GsonConverterFactory.create(gson))
            .build();

    EgeCalcApi.getUser getuser = retrofit.create(EgeCalcApi.getUser.class);
    return getuser;

}

public class UserLoginTask extends AsyncTask<Void, Void, Boolean> {

    private final String mLogin;
    private final String mPassword;
    private String mError = "1";
    private int i = 1;
    private EgeCalcApi.getUser getUser;
    private Account acc;
    UserLoginTask(String login, String password) throws UnsupportedEncodingException, NoSuchAlgorithmException {
        mLogin = login;
        mPassword = getHash(password);
        acc = new Account(mLogin, mPassword, "",0);
    }

    @Override
    protected Boolean doInBackground(Void... params) {
        // TODO: attempt authentication against a network service.
            Gson gson = new Gson();
            String str = gson.toJson(acc);
            getUser = AutirizationAPI.getApi();
            getUser.CurrUser(str).enqueue(new Callback<Info>() {
                @Override
                public void onResponse(@NonNull Call<Info> call, @NonNull Response<Info> response) {
                    System.out.print(response.body());
                    Info info = response.body();
                    assert info != null;
                    mError = info.getInformation();
                    System.out.print(mError);
                    if (mError.equals("successful"))
                        i = 0;
                    else {
                        i = 1;
                    }
                }

                @Override
                public void onFailure(@NonNull Call<Info> call, @NonNull Throwable t) {
                    Toast.makeText(LoginActivity.this, "Ошибка сети" + t, Toast.LENGTH_SHORT).show();
                }
            });
            return i == 0;
    }

    @Override
    protected void onPostExecute(final Boolean success) {
        mAuthTask = null;
        showProgress(false);

        if (success) {
            Intent i = new Intent(LoginActivity.this, MainActivity.class);
            startActivity(i);
            finish();
        } else {
            if(mError.equals("invalid password")) {
                mPasswordView.setError(mError);
                mPasswordView.requestFocus();
            }
            else if(mError.equals("invalid username")){
                mEmailView.setError(mError);
                mEmailView.requestFocus();
            }
        }
    }

    @Override
    protected void onCancelled() {
        mAuthTask = null;
        showProgress(false);
    }
}

@Override
protected Boolean doInBackground(Void... params) {
        // ...
        getUser.CurrUser(str).enqueue(new Callback<Info>() { // Строчка (*)
            // Весь код ниже будет выполнен асинхронно
            @Override
            public void onResponse(@NonNull Call<Info> call, @NonNull Response<Info> response) {
                System.out.print(response.body());
                Info info = response.body();
                assert info != null;
                mError = info.getInformation();
                System.out.print(mError);
                if (mError.equals("successful"))
                    i = 0;
                else {
                    i = 1;
                }
            }

            @Override
            public void onFailure(@NonNull Call<Info> call, @NonNull Throwable t) {
                Toast.makeText(LoginActivity.this, "Ошибка сети" + t, Toast.LENGTH_SHORT).show();
            }

        // Весь код выше будет выполнен асинхронно
        });

        // Эта строчка выполнится сразу же
        // после строчки (*)
        return i == 0;
}