Error: Couldn't connect to OAuth Server at localhost When Connect To Google BigQuery Since 2020.3

Issue

Upon connecting to Google BigQuery from Tableau Desktop 2020.3 (and later) where a proxy server is configured, the following error occurs:

Error: Couldn't connect to OAuth Server at localhost

Environment

Tableau Desktop 2020.3 and later
Google BigQuery

Resolution

Option 1

Delete the environment variables HTTP_PROXY and HTTPS_PROXY

Option 2

Use a batch file like bellow to launch Tableau Desktop. (This will disable the environment variables for the proxy setting)

------ tab_exec.bat -------------------
@echo off

set HTTP_PROXY=
set HTTPS_PROXY=

start "" "C:\Program Files\Tableau\Tableau 2020.4\bin\tableau.exe"
----------------------------------------

Option 3

Set an exception so that the proxy server will not be used for communicating with localhost via Internet Option in IE as described in the article below.
Tableau Fails To Connect to Amazon Athena through Proxy With Error Code 37CE01A3

Cause

On Tableau Desktop 2020.3 and later, the design for connecting to Google BigQuery changed, and it uses an additional java process to connect to Google BigQuery,. This java process is responsible for connecting to GBQ as well as communicating to Tableau Desktop using local port.
If there is a proxy server configured on the machine where Tableau Desktop is running, the java process will try to communicate with Tableau Desktop via proxy server and fails.