golang no Go files

root@ubuntu:~/kata/images# go get github.com/kata-containers/agent github.com/kata-containers/osbuilder
package github.com/kata-containers/osbuilder: no Go files in /opt/gopath/src/github.com/kata-containers/osbuilder
root@ubuntu:~/kata/images# ls /opt/gopath/src/github.com/kata-containers
agent  osbuilder  proxy  runtime  shim
root@ubuntu:~/kata/images# cd  /opt/gopath/src/github.com/kata-containers/osbuilder/
root@ubuntu:/opt/gopath/src/github.com/kata-containers/osbuilder# ls
CODE_OF_CONDUCT.md  dockerfiles  image-builder   LICENSE   README.md       scripts  VERSION
CONTRIBUTING.md     dracut       initrd-builder  Makefile  rootfs-builder  tests
root@ubuntu:/opt/gopath/src/github.com/kata-containers/osbuilder# 

root@ubuntu:~/kata/images# cd  /opt/gopath/src/github.com/kata-containers/osbuilder/
root@ubuntu:/opt/gopath/src/github.com/kata-containers/osbuilder# ls
CODE_OF_CONDUCT.md  dockerfiles  image-builder   LICENSE   README.md       scripts  VERSION
CONTRIBUTING.md     dracut       initrd-builder  Makefile  rootfs-builder  tests
root@ubuntu:/opt/gopath/src/github.com/kata-containers/osbuilder# make && make install 
Creating rootfs for centos
/opt/gopath/src/github.com/kata-containers/osbuilder/rootfs-builder/rootfs.sh -o 1.12.0-alpha1-88dbc2cd6f3840da8b104dc7df1cecaead88558a -r /opt/gopath/src/github.com/kata-containers/osbuilder/centos_rootfs centos
INFO: Detecting agent go version
INFO: Detecting runtime version using https://raw.githubusercontent.com/kata-containers/agent/master/VERSION