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

$ go version
go version go1.12.9 linux/amd64

Does this issue reproduce with the latest release?

Not tested with latest 1.13

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

$ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build945518265=/tmp/go-build -gno-record-gcc-switches"

What did you do?

package main

import (
"fmt"
)

var testStr string

func main() {
if testStr != "" {
fmt.Println("Not empty")
}
testStr := "Test string"
fmt.Println(testStr)
}

What did you expect to see?

After executing the following command, I would expect to throw error related to shadowing
$ go vet -vettool=$(which shadow)
$

What did you see instead?

Nothing was printed as output