From 2021-08-13, GitHub is no longer accepting account passwords when authenticating Git operations. You need to add a PAT (Personal Access Token) instead, and you can follow the below method to add a PAT on your system.

Create Personal Access Token on GitHub
From your GitHub account, go to Settings → Developer Settings → Personal Access Token → Generate New Token (Give your password) → Fillup the form → click Generate token → Copy the generated Token, it will be something like ghp_sFhFsSHhTzMDreGRLjmks4Tzuzgthdvfsrta

Now follow the below method based on your machine:

For Windows OS ⤴
Go to Credential Manager from Control Panel → Windows Credentials → find git:https://github.com → Edit → On Password replace with with your GitHub Personal Access Token → You are Done

If you don’t find git:https://github.com → Click on Add a generic credential → Internet address will be git:https://github.com and you need to type in your username and password will be your GitHub Personal Access Token → Click Ok and you are done

For macOS ⤴
Click on the Spotlight icon (magnifying glass) on the right side of the menu bar. Type Keychain access then press the Enter key to launch the app → In Keychain Access, search for github.com → Find the internet password entry for github.com → Edit or delete the entry accordingly → You are done

For a Linux-based OS ⤴
For Linux, you need to configure the local GIT client with a username and email address,

$ git config --global user.name "your_github_username"
$ git config --global user.email "your_github_email"
$ git config -l

Once GIT is configured, we can begin using it to access GitHub. Example:

$ git clone https://github.com/YOUR-USERNAME/YOUR-REPOSITORY
> Cloning into `YOUR-REPOSITORY`...
Username: <type your username>
Password: <type your password or personal access token (GitHub)

Now cache the given record in your computer to remembers the token:

$ git config --global credential.helper cache

If needed, anytime you can delete the cache record by:

$ git config --global --unset credential.helper
$ git config --system --unset credential.helper