Embed go exp package requirements to ensure we don't use arbitrary exp, move utilities to utils

utils/unix.go

@@ -0,0 +1,19 @@
+package utils
+
+import "net/http"
+
+// UnixRoundTripper https://github.com/oauth2-proxy/oauth2-proxy/blob/master/pkg/upstream/http.go#L124
+type UnixRoundTripper struct {
+	Transport *http.Transport
+}
+
+// RoundTrip set bare minimum stuff
+func (t UnixRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
+	req = req.Clone(req.Context())
+	if req.Host == "" {
+		req.Host = "localhost"
+	}
+	req.URL.Host = req.Host // proxy error: no Host in request URL
+	req.URL.Scheme = "http" // make http.Transport happy and avoid an infinite recursion
+	return t.Transport.RoundTrip(req)
+}