Go，Golang：使用GOROOT导入外部包(Go, Golang : external package import with GOROOT)

I am trying to go to next step but keep getting errors

1. I have the package that I want to import ready.
2. All I need to do is to import the external package from github and be able to use it on any code.

So this is what I did.

mkdir $HOME/go
export GOPATH=$HOME/go
go get github.com/user/project

This runs successfully. I downloaded it onto here with source code files from github

/Users/user/go/src/github.com/user/project/project.go

So to use this package that I just import I do

go run /Users/user/Desktop/code.go

But I am getting the following errors

 MacBook-Air:~ user$ go run /Users/user/Desktop/code.go 
 Desktop/code.go:32:8: cannot find package "project" in any of:
        /usr/local/go/src/pkg/project (from $GOROOT)
        /Users/user/go/src/project (from $GOPATH)

What should I do? AM I missing something? Thanks in advance and please help me. I wrote a lot of code but being very frustrated not being able to distribute it because of this.