Migrate to go modules

Author: typeless

CONTRIBUTING.md

@@ -77,7 +77,7 @@ your working directory and it will try to run the test suite locally.
 ## Vendoring
 
 We keep a cached copy of dependencies within the `vendor/` directory,
-managing updates via [dep](https://github.com/golang/dep).
+managing updates via [Modules](https://golang.org/cmd/go/#hdr-Module_maintenance).
 
 Pull requests should only include `vendor/` updates if they are part of
 the same change, be it a bugfix or a feature addition.
@@ -86,7 +86,7 @@ The `vendor/` update needs to be justified as part of the PR description,
 and must be verified by the reviewers and/or merger to always reference
 an existing upstream commit.
 
-You can find more information on how to get started with it on the [dep project website](https://golang.github.io/dep/docs/introduction.html).
+You can find more information on how to get started with it on the [Modules Wiki](https://github.com/golang/go/wiki/Modules).
 
 ## Translation