Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go version go1.10.3 darwin/amd64 vgo:2018-02-20.1

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN="/Users/morlay/Go/bin"
GOCACHE="/Users/morlay/Library/Caches/go-build"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/morlay/Go"
GORACE=""
GOROOT="/usr/local/Cellar/go/1.10.3/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.10.3/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/l1/sr0pz92x5n7fwmdjszmjfcrc0000gn/T/go-build681411572=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Here the example https://github.com/go-courier/enumeration

github.com/go-courier/enumeration/
   generator/
      go.mod
   go.mod

We often create a monorepo with to assemble all related packages. but we use them for different purpose.

As the example,

• The root package github.com/go-courier/enumeration as core modules.
• The github.com/go-courier/enumeration/generator for go generate.

They have different dependences, and we couldn't put all dependences into the go.mod in root package, because we don't want to includes unnecessary dependences when we just use github.com/go-courier/enumeration

However, after we added go.mod under github.com/go-courier/enumeration/generator to isolate their owner dependences. The problem comes.

github.com/go-courier/enumeration/generator requires github.com/go-courier/enumeration
and we have to commit root codes first as one version,
and commit again just with upgrading dependences of github.com/go-courier/enumeration/generator to solve dependences issue of sub package.

This may make a little trouble for maintaining monorepo.

Could we let sub packages use the same version of root package. with marking version ~ or other token?

like below:

module github.com/go-courier/enumeration/generator

require (
	github.com/go-courier/enumeration ~
        ...
)

meanings sub package github.com/go-courier/enumeration/generator will use the same version of
github.com/go-courier/enumeration