$go get golang.org/x/tools/cmd/goimports

$go get golang.org/x/crypto/sha3
package golang.org/x/crypto/sha3: unrecognized import path "golang.org/x/crypto/sha3" (https fetch: Get https://golang.org/x/crypto/sha3?go-get=1: dial tcp 216.239.37.1:443: i/o timeout)

$cd $GOPATH/golang.org/x
$git clone https://github.com/golang/crypto.git