https://www.socketloop.com/tutorials/golang-copy-directory-including-sub-directories-files

copydir.go

package main

 import (
   "os"
   "flag"
   "fmt"
   "io"
 )



 func CopyFile(source string, dest string) (err error) {
     sourcefile, err := os.Open(source)
     if err != nil {
         return err
     }

     defer sourcefile.Close()

     destfile, err := os.Create(dest)
     if err != nil {
         return err
     }

     defer destfile.Close()

     _, err = io.Copy(destfile, sourcefile)
     if err == nil {
         sourceinfo, err := os.Stat(source)
         if err != nil {
             err = os.Chmod(dest, sourceinfo.Mode())
         }

     }

     return
 }

 func CopyDir(source string, dest string) (err error) {

     // get properties of source dir
     sourceinfo, err := os.Stat(source)
     if err != nil {
         return err
     }

     // create dest dir

     err = os.MkdirAll(dest, sourceinfo.Mode())
     if err != nil {
         return err
     }

     directory, _ := os.Open(source)

     objects, err := directory.Readdir(-1)

     for _, obj := range objects {

         sourcefilepointer := source + "/" + obj.Name()

         destinationfilepointer := dest + "/" + obj.Name()


         if obj.IsDir() {
             // create sub-directories - recursively
             err = CopyDir(sourcefilepointer, destinationfilepointer)
             if err != nil {
                 fmt.Println(err)
             }
         } else {
             // perform copy
             err = CopyFile(sourcefilepointer, destinationfilepointer)
             if err != nil {
                 fmt.Println(err)
             }
         }

     }
     return
 }




 func main() {
   flag.Parse() // get the source and destination directory

   source_dir := flag.Arg(0) // get the source directory from 1st argument

   dest_dir := flag.Arg(1) // get the destination directory from the 2nd argument

   fmt.Println("Source :" + source_dir)

   // check if the source dir exist
   src, err := os.Stat(source_dir)
   if err != nil {
      panic(err)
   }

   if !src.IsDir() {
     fmt.Println("Source is not a directory")
     os.Exit(1)
   }

   // create the destination directory
   fmt.Println("Destination :"+ dest_dir)

   _, err = os.Open(dest_dir)
   if !os.IsNotExist(err) {
     fmt.Println("Destination directory already exists. Abort!")
     os.Exit(1)
   }

   err = CopyDir(source_dir, dest_dir)
   if err != nil {
      fmt.Println(err)
   } else {
      fmt.Println("Directory copied")
   }

 }