Doesn’t compile with go 1.12

[yuwash]

The README does state that you should use go 1.8, but it seems more recent versions don’t work. With go 1.12 I got

+ gofmt -w /home/yuwash/git/github-mgoltzsche/rkt-compose                                                                                              
+ mkdir -p build/src/github.com/mgoltzsche/rkt-compose                                                                                                 
+ ln -sf /home/yuwash/git/github-mgoltzsche/rkt-compose/LICENSE /home/yuwash/git/github-mgoltzsche/rkt-compose/README.md /home/yuwash/git/github-mgoltz
sche/rkt-compose/build /home/yuwash/git/github-mgoltzsche/rkt-compose/checks /home/yuwash/git/github-mgoltzsche/rkt-compose/launcher /home/yuwash/git/g
ithub-mgoltzsche/rkt-compose/log /home/yuwash/git/github-mgoltzsche/rkt-compose/main.go /home/yuwash/git/github-mgoltzsche/rkt-compose/make.sh /home/yu
wash/git/github-mgoltzsche/rkt-compose/model /home/yuwash/git/github-mgoltzsche/rkt-compose/test-resources /home/yuwash/git/github-mgoltzsche/rkt-compo
se/build/src/github.com/mgoltzsche/rkt-compose/                                                                                                        
+ rm /home/yuwash/git/github-mgoltzsche/rkt-compose/build/src/github.com/mgoltzsche/rkt-compose/build                                                  
+ export GOPATH=/home/yuwash/git/github-mgoltzsche/rkt-compose/build                                                                                   
+ go get gopkg.in/yaml.v2                                                                                                                              
+ go get gopkg.in/appc/docker2aci.v0                                                                                                                   
+ go build -o bin/rkt-compose github.com/mgoltzsche/rkt-compose                                                                                        
+ go test github.com/mgoltzsche/rkt-compose/checks                                                                                                     
ok      github.com/mgoltzsche/rkt-compose/checks        0.156s                                                                                         
+ go test github.com/mgoltzsche/rkt-compose/model                                                                                                      
ok      github.com/mgoltzsche/rkt-compose/model 0.028s                                                                                                 
+ go test github.com/mgoltzsche/rkt-compose/launcher                                                                                                   
# github.com/mgoltzsche/rkt-compose/launcher                                                                                                           
build/src/github.com/mgoltzsche/rkt-compose/launcher/loader.go:266:7: redundant and: ex.Target == p.Target && ex.Target == p.Target                    
build/src/github.com/mgoltzsche/rkt-compose/launcher/launcher.go:287:10: Errorf format %s has arg buf of wrong type bytes.Buffer                       
FAIL    github.com/mgoltzsche/rkt-compose/launcher [build failed]