yarn 'There appears to be trouble with your network connection. Retrying...'

I'm working behind my institute proxy and can't use yarn, its showing

yarn install v1.16.0
info No lockfile found.
[1/4] Resolving packages...
info There appears to be trouble with your network connection. Retrying...

npm install giving me this error

network tunneling socket could not be established, statusCode=503

Yarn version 1.16.0; node version 8.10.0; npm version 3.5.2; ubuntu 18.04.02

What I have done so far:

1. set proxy in /etc/apt/apt.conf and /etc/environment

   Acquire::http::proxy "http://username:password@proxy:port";
   Acquire::https::proxy "http://username:password@proxy:port";
   Acquire::ftp::proxy "http://username:password@proxy:port";

2. set proxy in .bashrc

   export http_proxy="http://username:password@proxy:port";
   export https_proxy="http://username:password@proxy:port";
   export HTTPS_PROXY="http://username:password@proxy:port"
   export HTTP_PROXY="http://username:password@proxy:port"

3. yarn install --network-timeout 100000

4. yarn config set proxy http://username:password@host:port
   yarn config set https-proxy http://username:password@host:port

5. with npm

   npm config set registry http://registry.npmjs.org/
   npm config set proxy http://username:mypassword@proxy:port
   npm config set https-proxy http://username:mypassword@proxy:port
   npm config set strict-ssl false
   npm --proxy http://myusername:mypassword@proxy.us.somecompany:8080 --without-ssl --insecure -g install

6. Did all of these mentioned here https://github.com/yarnpkg/yarn/issues/5259#issuecomment-379769451
7. Did all these Is there a way to make npm install (the command) to work behind proxy?

None of them fixed the problem. How do I make yarn work in this case?

from yarn 'There appears to be trouble with your network connection. Retrying...'