How to use self defined package - go

Question

I have follow two simple go files
main.go
package main
import "fmt"
import "go-package/math"
func main() {
xs := []float64{1, 2, 3, 4}
avg := math.Average(xs)
fmt.Println(avg)
}
mymath.go
package math
func Average(xs []float64) float64 {
total := float64(0)
for _, x := range xs {
total += x
}
return total / float64(len(xs))
}
The file and directory structure is:
$GOPATH
src
go-package
math
mymath.go
main.go
When I navigate to $GOPATH/src/go-package, and open the terminal and run the command: go run main.go, the result is printed out.
Then, I navigate to $GOPATH/src/go-package/math, and run the command go install, and the package successfully installed at $GOPATH\pkg\windows_amd64\go-package\math.a
Then I navigate back to $GOPATH/src/go-package, and remove the math directoy,
I rerun the command go run main.go, error occurs:
main.go:4:8: cannot find package "go-package/math" in any of:
D:\softwareInstalled\Go\src\go-package\math (from $GOROOT)
D:\softwareInstalled\Go\GoPath\src\go-package\math (from $GOPATH)
I have put the math package at $GOPATH\pkg\windows_amd64\go-package\math.a
I wonder why Go doesn't pick up the package from this directory.
And how can I use math.a?Where should I place it?

Answer 1

Golang uses the source files of your imported packages. So when you wanna use the package go-package/math inside your main.go, you should not delete the source files from src/go-package/math. Leave them inside your project and everything's good.
Besides, go get also loads source files into your $GOPATH/src folder. Hope this helps.