How to reset or change the passphrase for a GitHub SSH key?

If you had generate a SSH-key with passphrase and then you forget your passphrase for this SSH-key,there’s no way to recover it, You’ll need to generate a brand new SSH keypair or switch to HTTPS cloning so you can use your GitHub password instead.

BUT，there are exceptions

If you configured your SSH passphrase with the OS X Keychain, you may be able to recover it.

1. In Finder, search for the Keychain Access app.
2. In Keychain Access, search for SSH.
3. Double click on the entry for your SSH key to open a new dialog box.
4. Keychain access dialogIn the lower-left corner, select Show password.
5. You’ll be prompted for your administrative password. Type it into the “Keychain Access” dialog box.
6. Your password will be revealed.

Refer to Github help – How do I recover my SSH key passphrase?