env GO111MODULE=on

go get x
go list -m all
stdout 'rsc.io/breaker v2.0.0\+incompatible'

cp go.mod2 go.mod
go get rsc.io/breaker@7307b30
go list -m all
stdout 'rsc.io/breaker v2.0.0\+incompatible'

go get rsc.io/breaker@v2.0.0
go list -m all
stdout 'rsc.io/breaker v2.0.0\+incompatible'

-- go.mod --
module x

-- go.mod2 --
module x
require rsc.io/breaker v1.0.0

-- x.go --
package x
import "rsc.io/breaker"
var _ = breaker.XX