There is a bug in go standard library.

Create a new file named main.go, and put following code in it: 

package main

import "fmt"

func main() {
    fmt.Println("Hello world!")
}

Save it and run "go vet main.go", then it will return following result:

vet: import failed: reading export data: /usr/lib64/go/pkg/linux_amd64/fmt.a:
go archive is missing __.PKGDEF
vet: import failed: reading export data: /usr/lib64/go/pkg/linux_amd64/fmt.a:
go archive is missing __.PKGDEF
exit status 1

Run "head -2 /usr/lib64/go/pkg/linux_amd64/fmt.a", and it will return:

!<arch>
__.PKGDEF/      0           399   399   100644  3208      `

You can find that there is a extra char "/" after the word "__.PKGDEF" in the
second line. It causes go can't import library.

There is a correct library in my computer which it's first two lines should be
as follow.

$ head -2 $GOPATH/pkg/linux_amd64/golang.org/x/tools/imports.a 
!<arch>
__.PKGDEF       0           0     0     644     838       `