title: go) how to i make download service?
body: <p>i make upload server
  but i can't make download server</p>
  
  <pre><code>package main
  
  import (
      "fmt"
      "io"
      "os"
  
      "github.com/gin-gonic/gin"
  )
  
  func uploadHandler(c *gin.Context) {
      uid := c.Request.FormValue("uid")
      file, header, err := c.Request.FormFile("uploadFile")
      filename := header.Filename
      fmt.Println(filename)
      err = os.Mkdir("./upload/"+uid, 777)
      out, err := os.Create("./upload/" + uid + "/" + filename)
      _, err = io.Copy(out, file)
  }
  
  func main() {
      r := gin.Default()
      r.POST("/goupload", uploadHandler)
      r.POST("/godownload", downloadHandler)
      // listen and server on 0.0.0.0:8080
      r.Run()
  }
  </code></pre>
  
  <p>so, how to i make download server?</p>
  
  <p>i will use post uid &amp; downloadfilename.</p>