$ cat test.go
package main

import (
        "fmt"
        "pack1"
)

func main() {
        fmt.Println(pack1.DoSmth())
}
$ ls $GOPATH/pkg/linux_amd64
$ go build test.go
$ ls $GOPATH/pkg/linux_amd64
$ go install pack1
$ ls $GOPATH/pkg/linux_amd64
pack1.a