You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: ticketsender.go
    path of file: ./repos/plik/vendor/github.com/google/s2a-go/internal/record
    
    the code of the file until where you have to start completion: /*
 *
 * Copyright 2021 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writin
    
func (t *ticketSender) getAuthMechanisms() []*s2apb.AuthenticationMechanism {
	if t.tokenManager == nil {
		return nil
	}
	// First handle the special case when no local identity has been provided
	// by the application. In this case, an AuthenticationMechanism with no local
	// identity will be sent.
	if t.localIdentity == nil {
		token, err := t.tokenManager.DefaultToken()
		if err != nil {
			grpclog.Infof("unable to get token for empty local identity: %v", err)
			return nil
		}
		return []*s2apb.AuthenticationMechanism{
			{
				MechanismOneof: &s2apb.AuthenticationMechanism_Token{
					Token: token,
				},
			},
		}
	}

	// Next, handle the case where the application (or the S2A) has specified
	// a local identity.
	token, err := t.tokenManager.Token(t.localIdentity)
	if err != nil {
		grpclog.Infof("unable to get token for local identity %v: %v", t.localIdentity, err)
		return nil
	}
	return []*s2apb.AuthenticationMechanism{
		{
			Identity: t.localIdentity,
			MechanismOneof: &s2apb.AuthenticationMechanism_Token{
				Token: token,
			},
		},
	}
}