ci: accommodate go1.16 changes to go mod (#4102)
ci: accommodate go1.16 changes to go mod (#4102)

As of go1.16, the `go` commands will no longer make automatic changes to go.{mod,sum} files (see: https://blog.golang.org/go116-module-changes). This broke the release script which relied on `go mod download` and/or `go build` to automatically generate the go.sum file. This commit explicitly invokes `go mod tidy` to have the go.sum file generated.
l3dlp/caddy,l3dlp/caddy,mholt/caddy,l3dlp/caddy,mholt/caddy