Update dependencies

vendor/github.com/gorilla/csrf/context.go

@@ -0,0 +1,28 @@
+//go:build go1.7
+// +build go1.7
+
+package csrf
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+)
+
+func contextGet(r *http.Request, key string) (interface{}, error) {
+	val := r.Context().Value(key)
+	if val == nil {
+		return nil, fmt.Errorf("no value exists in the context for key %q", key)
+	}
+	return val, nil
+}
+
+func contextSave(r *http.Request, key string, val interface{}) *http.Request {
+	ctx := r.Context()
+	ctx = context.WithValue(ctx, key, val) // nolint:staticcheck
+	return r.WithContext(ctx)
+}
+
+func contextClear(r *http.Request) {
+	// no-op for go1.7+
+}