staticcheck: flag strings.HasSuffix with a RequestURI

[ainar-g]

Using strings.HasSuffix with http.Request.RequestURI probably doesn't do what the programmer thinks it does and can be unsafe. For example, this code:

if strings.HasSuffix(r.RequestURI, "/admin") {
	http.Error(w, "forbidden", http.StatusForbidden)

	return
}

Will do nothing, if the user makes a request for /admin?unsafe=1.

There is some potential here for false positives, but I don't think it's that high, and the code in question should probably be rewritten either way. At the very least, looking for pathlike patterns in the RequestURI field is very likely an error.