code: func (r *keyring) Signers() ([]ssh.Signer, error) {
  	r.mu.Lock()
  	defer r.mu.Unlock()
  	if r.locked {
  		return nil, errLocked
  	}
  
  	s := make([]ssh.Signer, 0, len(r.keys))
  	for _, k := range r.keys {
  		s = append(s, k.signer)
  	}
  	return s, nil
  }
docs: // Signers returns signers for all the known keys.