How do you setup SSH Forwarding (?) so you can use specific account with github

[hinate13]

Context:
I have multiple accounts (eg work vs personal) I use for sites (eg, github.com). Each are tied to different SSH keys. I'm on Windows, but setup devContainers to wrap my projects. Some are for personal, and some for work. Within the host, I can just configure multiple accounts like so:

~/.ssh/config:

Host github.com
    HostName github.com
    User git
    IdentityFile ~/.ssh/github/personal-account

Host work-github
    HostName github.com
    User git
    IdentityFile ~/.ssh/github/work-account

If I do a normal clone from github using git clone command, it will use my personal account. If I want to clone down using my work profile, it will be like so:

git clone git@work-github/my-account/project-a.git

Problem:
When I use a devContainer, I setup ssh-forwarding so I can add keys and not have it stored into the container image. However, if I try the git clone using work account, it will not find the correct SSH key to use. I can confirm the keys are forwarded (using ssh-add -l). I could also try to create ~/.ssh/config and tell it to use a specific key -- but it will require a link to a private key file that doesn't exist inside the devContainer. Is there a way to link the IdentityFile to the key forwarded from ssh-forwarding? Or what other options do people do to work around this? Ideally I don't want to be having my private key stored/copied in multiple places on my system and containers.