~/.ssh/config and ~/.gitconfig to work with multiple github accounts in one machine. you're welcome~~~

gitconfig

[url "git@private1.github.com:someuser/private-repo-1"]
        insteadOf = https://github.com/someuser/private-repo-1

[url "git@private2.github.com:someuser/private-repo-2"]
        insteadOf = https://github.com/someuser/private-repo-2
[url "git@customName.github.com:keepThis"]
	insteadOf = git@github.com:keepThis

ssh_config

Host github.com
   HostName github.com
   User git
   IdentityFile ~/.ssh/id_ed25519
   PreferredAuthentications publickey
   AddKeysToAgent yes
   IdentitiesOnly yes
#arbitrary, just change in your git remote url github.com to this arbitrary host
#i.e. git remote set-url origin git@dump.github.com:some-github-account/repo.git
Host dump.github.com 
   HostName github.com
   User git
   IdentityFile ~/.ssh/another_id_ed25519
   PreferredAuthentications publickey
   AddKeysToAgent yes
   IdentitiesOnly yes
Host gitlab.custom.port
   HostName gitlab.com
   User git
   Port 30000 #custom port
   IdentityFile /home/mo/.ssh/rsa_key
   PreferredAuthentications publickey
   AddKeysToAgent yes
   IdentitiesOnly yes

#when generating ssh-key-gen, you should start ssh-agent then add newly created key to ssh-agent, after that can you add it to github or gitlab
#to download private go modules:
#git config --global url."ssh://git@your_gitlab_endpoint_without_port_becsuse_you_add_Port_above".insteadOf "http://your_gitlab_endpoint_without_port_becsuse_you_add_Port_above"
#go env -w GOPRIVATE=your_gitlab_endpoint:your_custom_port_if_exist