Update go1.12 -> go1.13 + update dependencies + mod tidy

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.12-alpine as builder
+FROM golang:1.13-alpine as builder
 
 # Setup
 RUN mkdir -p /go/src/github.com/thomseddon/traefik-forward-auth

go.mod

@@ -1,39 +1,26 @@
 module github.com/thomseddon/traefik-forward-auth
 
-go 1.12
+go 1.13
 
 require (
-	github.com/VividCortex/gohistogram v1.0.0 // indirect
-	github.com/cenkalti/backoff v2.1.1+incompatible // indirect
-	github.com/containous/alice v0.0.0-20181107144136-d83ebdd94cbd // indirect
-	github.com/containous/flaeg v1.4.1 // indirect
-	github.com/containous/mux v0.0.0-20181024131434-c33f32e26898 // indirect
-	github.com/containous/traefik v2.0.0-alpha2+incompatible
+	github.com/containous/traefik/v2 v2.1.2
 	github.com/coreos/go-oidc v2.1.0+incompatible
-	github.com/go-acme/lego v2.5.0+incompatible // indirect
-	github.com/go-kit/kit v0.8.0 // indirect
-	github.com/gorilla/context v1.1.1 // indirect
-	github.com/gravitational/trace v0.0.0-20190409171327-f30095ced5ff // indirect
-	github.com/jessevdk/go-flags v1.4.1-0.20181221193153-c0795c8afcf4
-	github.com/jonboulle/clockwork v0.1.0 // indirect
-	github.com/konsorten/go-windows-terminal-sequences v1.0.2 // indirect
-	github.com/kr/pretty v0.1.0 // indirect
-	github.com/kr/pty v1.1.4 // indirect
-	github.com/miekg/dns v1.1.8 // indirect
-	github.com/patrickmn/go-cache v2.1.0+incompatible // indirect
-	github.com/pkg/errors v0.8.1 // indirect
 	github.com/pquerna/cachecontrol v0.0.0-20180517163645-1555304b9b35 // indirect
-	github.com/ryanuber/go-glob v1.0.0 // indirect
-	github.com/sirupsen/logrus v1.4.1
-	github.com/stretchr/objx v0.2.0 // indirect
-	github.com/stretchr/testify v1.3.0
+	github.com/sirupsen/logrus v1.4.2
+	github.com/stretchr/testify v1.4.0
 	github.com/thomseddon/go-flags v1.4.1-0.20190507184247-a3629c504486
-	github.com/vulcand/predicate v1.1.0 // indirect
-	golang.org/x/crypto v0.0.0-20190422183909-d864b10871cd // indirect
-	golang.org/x/net v0.0.0-20190420063019-afa5a82059c6 // indirect
 	golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45
-	golang.org/x/sync v0.0.0-20190423024810-112230192c58 // indirect
-	golang.org/x/sys v0.0.0-20190422165155-953cdadca894 // indirect
-	gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 // indirect
 	gopkg.in/square/go-jose.v2 v2.3.1
 )
+
+// From traefik
+replace (
+	github.com/Azure/go-autorest => github.com/Azure/go-autorest v12.4.1+incompatible
+	github.com/abbot/go-http-auth => github.com/containous/go-http-auth v0.4.1-0.20180112153951-65b0cdae8d7f
+	github.com/docker/docker => github.com/docker/engine v1.4.2-0.20191113042239-ea84732a7725
+	github.com/go-check/check => github.com/containous/check v0.0.0-20170915194414-ca0bf163426a
+	github.com/gorilla/mux => github.com/containous/mux v0.0.0-20181024131434-c33f32e26898
+	github.com/mailgun/minheap => github.com/containous/minheap v0.0.0-20190809180810-6e71eb837595
+	github.com/mailgun/multibuf => github.com/containous/multibuf v0.0.0-20190809014333-8b6c9a7e6bba
+	github.com/rancher/go-rancher-metadata => github.com/containous/go-rancher-metadata v0.0.0-20190402144056-c6a65f8b7a28
+)