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

go version go1.11.4 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/bbytheway/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/bbytheway/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/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/00/vxd1fq_x3_367zzc4k6rs0km03gnm5/T/go-build500153777=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

I received an error from go vet when attempting to validate a custom errors package. It appears that there is a file loading order race condition with the custom package and the standard errors package.

I have created a repository with code that reproduces the issue.

https://github.com/bytheway/VetFailure

Essentially, go vet will return the error

./example_test.go:7: ExampleDemo refers to unknown identifier: Demo

when run bare, but if you feed the files to go vet in a reversed order, it passes.

This is probably related to having 2 files using the errors_test package, one of them also using the stdlib errors package (imported to a goErrors name). If the one importing stdlib errors comes first, go vet is unable to resolve the ExampleFunc() identifiers. If the order is reverse (examples, then the tests w/stdlib errors), then go vet passes.

What did you expect to see?

go vet should validate that the files are properly formed.

What did you see instead?

go vet detects a spurious error.