Go语言包结构

I am trying to learn Go and to follow the existing conventions, but, as every convention, you need to first understand them before use them well, and after some research, I didn't find an exact answer to my following question:

I've set up a project inside my $GOPATH, following a similar structure like this:

$GOPATH/
  github.com/
    username/
      projectname/
        main.go
        numbers/
          rational.go
          real.go
          complex.go

My main is:

package main

import(
"fmt"
"./numbers"
)

func main() {
    fmt.Println(numbers.Real{2.0})
}

So, the questions are:

1. I read that I need to have a file package.go inside each package folder, is that right ?

2. If so, inside numbers.go, how will I import rational.go, real.go and complex.go ?

3. And then, is it possible to have something like:

   // real.go
   package numbers
   
   type Real struct {
       Number float64
   }
   

... and in main do fmt.Println(numbers.Real{2.0}) ?

First: Your Setup misses the folder src: It should be `$GOPATH/src/github.com/..."

Second: Do not use relative imports. Just do not do it. Import package numbers like import "github.com/username/projectname/number"

To your questions:

1. No. If you have Go files in a folder the are combined to a package but you are not force to put a package into all folders.

2. All the files rational.go, complex.go and real.go would normally start with package numbers. The are all part of package numbers and you do not include files but packages. The current package need not be imported. So: No.

3. Yes