Remove go install error : errStdout and errStderr declared and not used

[pivaldi]

Fixe this problem and make this package a go module.

>  go install github.com/azer/yolo@latest
go: finding module for package github.com/gorilla/websocket
go: finding module for package github.com/azer/logger
go: finding module for package github.com/fsnotify/fsnotify
go: found github.com/azer/logger in github.com/azer/logger v1.0.0
go: found github.com/fsnotify/fsnotify in github.com/fsnotify/fsnotify v1.6.0
go: found github.com/gorilla/websocket in github.com/gorilla/websocket v1.5.0
# github.com/azer/yolo/src
code/go/pkg/mod/github.com/azer/yolo@v0.0.0-20200421082124-9f74cacbc50c/src/cli.go:27:6: errStdout declared and not used
code/go/pkg/mod/github.com/azer/yolo@v0.0.0-20200421082124-9f74cacbc50c/src/cli.go:27:17: errStderr declared and not used