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: roundtripper.go
    path of file: ./repos/gitlabhq/workhorse/internal/secret
    
    the code of the file until where you have to start completion: package secret

import (
	"net/http"
)

const (
	// This header carries the JWT token for gitlab-rails
	RequestHeader = "Gitlab-Workhorse-Api-Requ
    
func (r *roundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
	tokenString, err := JWTTokenString(DefaultClaims)
	if err != nil {
		return nil, err
	}

	// Set a custom header for the request. This can be used in some
	// configurations (Passenger) to solve auth request routing problems.
	req.Header.Set("Gitlab-Workhorse", r.version)
	req.Header.Set(RequestHeader, tokenString)

	return r.next.RoundTrip(req)
}