When importing a package with a non-canonical import path (ending in a slash), the compiler error tells you about it and points you to the offending import.

If the imported package imports a vendored package (and only then), the compiler error points to the wrong location and the error text is wrong too. See below in the expected/actual output.

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

go version go1.7 linux/amd64

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

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/opt/go"
GORACE=""
GOROOT="/opt/go_dist/go"
GOTOOLDIR="/opt/go_dist/go/pkg/tool/linux_amd64"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build865793365=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLEgo build ./...
# github.com/benma/test/lib/
lib/lib.go:3: non-canonical import path "github.com/benma/test//vendor/vendoredlib" (should be "github.com/benma/test/vendor/vendoredlib")
lib/lib.go:3: can't find import: "github.com/benma/test//vendor/vendoredlib"
D="1"

What did you do?

go build ./... in a project with those three files inside:

main.go:

package main

import "github.com/benma/test/lib/" // error here, but compiler points somewhere else!

var _ = lib.Foo

func main() {}

lib/lib.go:

package lib

import "vendoredlib"

var Foo = vendoredlib.Foo

vendor/vendoredlib/vendoredlib.go:

package vendoredlib

var Foo = true

What did you expect to see?

Compiler error like this:

go build ./...
# github.com/benma/test
./main.go:3: non-canonical import path "github.com/benma/test/lib/" (should be "github.com/benma/test/lib")
./main.go:3: can't find import: "github.com/benma/test/lib/"

What did you see instead?

go build ./...
# github.com/benma/test/lib/
lib/lib.go:3: non-canonical import path "github.com/benma/test//vendor/vendoredlib" (should be "github.com/benma/test/vendor/vendoredlib")
lib/lib.go:3: can't find import: "github.com/benma/test//vendor/vendoredlib"

Note that the error points to an import in lib.go, where everything is correct, instead of to main.go. Also the error text talks about github.com/benma/test//vendor/vendoredlib vs github.com/benma/test/vendor/vendoredlib, where the actual import in lib.go:3 is simply import "vendoredlib".

On a related note, shouldn't goimports fix wrong imports like that (and simply strip the trailing slash)?