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

$ go version
go version go1.12.5 linux/amd64

Does this issue reproduce with the latest release?

Yes

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

$ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/jaime/.cache/go-build"
GOEXE=""
GOFLAGS="-mod=vendor"
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/jaime/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_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=/tmp/go-build448668772=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I tried to install goimports from my home directory.

$ echo $GO111MODULE 
on
$ echo $GOFLAGS
-mod=vendor
$ pwd
/home/jaime
$ go get golang.org/x/tools/cmd/goimports
go get: disabled by -mod=vendor
$ 

What did you expect to see?

I expected the tool to work like it has for years. I expected go get to download and install goimports.

What did you see instead?

I got an error about -mod=vendor being on.

In my environment, we use vendoring. Because Go is moving away from dep and moving towards modules, we've started doing the work to migrate to modules.

A temporary work around for this bug is to do this.

GO111MODULE=off go get golang.org/x/tools/cmd/goimports