gvt was a minimalistic Go vendoring tool made for the vendor/ folder (once known as the
GO15VENDOREXPERIMENT).
It was based on gb-vendor by Dave Cheney.
Since Go 1.11, the go tool supports modules, a native solution to the dependency problem.
The go tool understands gvt manifest files, so you just have to run
GO111MODULE=on go mod init
GO111MODULE=on go mod vendor
to migrate and still populate the vendor/ folder for backwards compatibility.
Read more in the docs or on the wiki.
Modules support is experimental in 1.11, but it will probably serve you better than gvt would.
— So long, and thanks for all the fish!