How Can I Make the Go HTTP Client NOT Follow Redirects Automatically?

Another option, using the client itself, without the RoundTrip:

// create a custom error to know if a redirect happened
var RedirectAttemptedError = errors.New("redirect")

client := &http.Client{}
// return the error, so client won't attempt redirects
client.CheckRedirect = func(req *http.Request, via []*http.Request) error {
        return RedirectAttemptedError
}
// Work with the client...
resp, err := client.Head(urlToAccess)

// test if we got the custom error
if urlError, ok := err.(*url.Error); ok && urlError.Err == RedirectAttemptedError{
        err = nil   
}

UPDATE: this solution is for go < 1.7

There's a much simpler solution right now:

client := &http.Client{
    CheckRedirect: func(req *http.Request, via []*http.Request) error {
        return http.ErrUseLastResponse
    },
}

This way, the http package automatically knows: "Ah, I shouldn't follow any redirects", but does not throw any error. From the comment in the source code:

As a special case, if CheckRedirect returns ErrUseLastResponse, then the most recent response is returned with its body unclosed, along with a nil error.