tim@Tims-MacBook-Pro freno % go build cmd/freno/main.go         
go: inconsistent vendoring in /Users/tim/go/src/github.com/github/freno:
	github.com/armon/go-metrics@v0.0.0-20190430140413-ec5e00d3c878: is explicitly required in go.mod, but not marked as explicit in vendor/modules.txt
	github.com/boltdb/bolt@v1.3.1: is explicitly required in go.mod, but not marked as explicit in vendor/modules.txt
	github.com/bradfitz/gomemcache@v0.0.0-20190913173617-a41fca850d0b: is explicitly required in go.mod, but not marked as explicit in vendor/modules.txt
	github.com/go-sql-driver/mysql@v1.5.0: is explicitly required in go.mod, but not marked as explicit in vendor/modules.txt
	github.com/hashicorp/go-msgpack@v0.5.5: is explicitly required in go.mod, but not marked as explicit in vendor/modules.txt
	github.com/julienschmidt/httprouter@v1.3.0: is explicitly required in go.mod, but not marked as explicit in vendor/modules.txt
	github.com/outbrain/golib@v0.0.0-20180830062331-ab954725f502: is explicitly required in go.mod, but not marked as explicit in vendor/modules.txt
	github.com/patrickmn/go-cache@v2.1.0+incompatible: is explicitly required in go.mod, but not marked as explicit in vendor/modules.txt
	github.com/rcrowley/go-metrics@v0.0.0-20190826022208-cac0b30c2563: is explicitly required in go.mod, but not marked as explicit in vendor/modules.txt
	golang.org/x/sys@v0.0.0-20190602015325-4c4f7f33c9ed: is explicitly required in go.mod, but not marked as explicit in vendor/modules.txt
	vitess.io/vitess@v2.1.1+incompatible: is explicitly required in go.mod, but not marked as explicit in vendor/modules.txt

run 'go mod vendor' to sync, or use -mod=mod or -mod=readonly to ignore the vendor directory

Vendoring

When the main module contains a top-level vendor directory and its go.mod file specifies go 1.14 or higher, the go command now defaults to -mod=vendor for operations that accept that flag. A new value for that flag, -mod=mod, causes the go command to instead load modules from the module cache (as when no vendor directory is present).

When -mod=vendor is set (explicitly or by default), the go command now verifies that the main module's vendor/modules.txt file is consistent with its go.mod file.