add file copy function

util.go

@@ -2,6 +2,7 @@ package goutil
 
 import (
 	"errors"
+	"io"
 	"math"
 	"os"
 	"regexp"
@@ -43,3 +44,28 @@ func Mkdirp(p string) error {
 	}
 	return nil
 }
+
+// straight outta stackoverflow
+// https://stackoverflow.com/questions/21060945/simple-way-to-copy-a-file-in-golang
+func CopyFile(src, dst string) (err error) {
+	in, err := os.Open(src)
+	if err != nil {
+		return
+	}
+	defer in.Close()
+	out, err := os.Create(dst)
+	if err != nil {
+		return
+	}
+	defer func() {
+		cerr := out.Close()
+		if err == nil {
+			err = cerr
+		}
+	}()
+	if _, err = io.Copy(out, in); err != nil {
+		return
+	}
+	err = out.Sync()
+	return
+}