When running command sudo apt update and using a proxy configured on the Linux machine, you receive a timeout error

Create a new empty file to configure apt

$ sudo vi /etc/apt/apt.conf

In this new file insert the following:

Acquire::http::Proxy "http://user:password@proxyhost:port";

If you do not have any authentication on the proxy type following:

Acquire::http::Proxy "http://proxyhost:port";