通过http接收大文件

Question

I've trying to receive big (~25Mb) file via http. From "client" i've send this file via PHP and cUrl and trying to receive it from golang.
Here is code:

package main

import (
    "fmt"
    "net/http"
    "io/ioutil"
)

func handler(w http.ResponseWriter, r *http.Request) {
    buf, _ := ioutil.ReadAll(r.Body)
    fmt.Println(string(buf[:]))
}

func main() {
    http.HandleFunc("/", handler)
    http.ListenAndServe(":12100", nil)
}

In this case i can see my file in ioutil.ReadAll output. But if i trying to get only file contents, it is failed :(

package main

import (
    "fmt"
    "net/http"
    "io/ioutil"
)

func handler(w http.ResponseWriter, r *http.Request) {
    r.ParseMultipartForm(0)
    fmt.Println(r.FormValue("f"))
}


func main() {
    http.HandleFunc("/", handler)
    http.ListenAndServe(":12100", nil)
}

However file is small (~900Kb) everything is ok. What is right way to send big files via http?

Answer 1

Go will start writing large files to disk, so that they don't clog up memory. You can then use FormFile to get the a handle to the file on disk. When you are done you should close the handle and delete the temporary file with r.MultipartForm.RemoveAll().

All together:

func handler(w http.ResponseWriter, r *http.Request) {
    r.ParseMultipartForm(0)
    defer r.MultipartForm.RemoveAll()
    fi, info, err := r.FormFile("f")
    defer fi.Close()
    fmt.Printf("Recieved %v",info.Filename)
    //Do whatever with it
}