将文件错误复制到Golang中的stdin

Question

I'm using echo to build a web app for dokku management. It has a url router to handle tarfile deploying and my handler is bellow: package routers

import (
    "fmt"
    "github.com/labstack/echo"
    "io"
    "net/http"
    "os/exec"
)

// deploy app via tar file
func deployTarApp(c echo.Context) error {
    name := c.Param("name")
    file, ef := c.FormFile("file")
    if ef != nil || file == nil {
        return c.NoContent(http.StatusBadRequest)
    }
    tempfile, et := file.Open()
    if et != nil {
        return c.JSON(http.StatusInternalServerError, et)
    }
    cmd := exec.Command(DokkuPath, "tar:in", name)
    stdin, err := cmd.StdinPipe()
    if err != nil {
        return c.JSON(http.StatusInternalServerError, err)
    }
    go func() {
        defer stdin.Close()
        io.Copy(stdin, tempfile)
    }()
    out, e := cmd.CombinedOutput()
    if e != nil {
        fmt.Println(string(out), e)
        return c.JSON(http.StatusInternalServerError, e)
    }
    return c.NoContent(http.StatusOK)
}

First get the form file, then copy it to stdin, then run dokku tar:in app-name. But the code throws an error

/var/lib/dokku/plugins/available/git/functions: line 114: /home/dokku/node-sample/refs/heads/master: No such file or directory
 exit status 128

What is the problem with the handler? I am new to golang, so I am not so familiar with it. Thanks for your help.