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

$ go version
go version go1.11.1 darwin/amd64

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

$ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/qiantao/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/qiantao/work/GoTestSrc"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/Cellar/go/1.11.1/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.11.1/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD=""
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/c7/4l8jfrp1699b8mhj2qjltwjr0000gn/T/go-build796658272=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

We have two project : lib-a and project-a

the project-a import lib-a ; if we need Implement a new feature ；
we checkout two new branches : lib-a-love-feature and project-a-love-feature

and project-a-love-feature import the codes in lib-a-love-feature

so go.mod in project-a-love-feature must is

module git.hezi.com/qiantao/project-a

require (
	git.hezi.com/qiantao/lib-a lib-a-love-feature
	github.com/go-log/log v0.1.0
	github.com/micro/go-micro v0.24.0
	rsc.io/quote v1.5.2
)

after go run main.go

go.mod in project-a-love-feature updated like this

module git.hezi.com/qiantao/project-a

require (
	git.hezi.com/qiantao/lib-a v0.0.0-20190321071845-f40956c1bfe6
	github.com/go-log/log v0.1.0
	github.com/micro/go-micro v0.24.0
	rsc.io/quote v1.5.2
)

v0.0.0-20190321071845-f40956c1bfe6 is a latest version for branch lib-a-love-feature

next !!
we push new codes to branch lib-a-love-feature

but in branch project-a-love-feature, because the go.mod is modified, we do not get the new codes!

have any way to keep go.mod