gin-gonic中的分段文件上传验证

Question

I am trying to add validation for the go based web application based on GIN framework. On the web page I am selecting a file and submitting and the server is processing it. On the server side I am try to add validation to check if the file has been given or not. If not then redirect back to original page.

    func panic(err error)  {
        if err != nil {
            log.Println(err)
        }
    }

    func displayTable (c *gin.Context) {    
    file, _ , err := c.Request.FormFile("file")
    panic(err)
    if file == nil {
        log.Println("File is nil.")
        log.Println(err)
        log.Println("*****")
        c.HTML(http.StatusInternalServerError, "index.tmpl", gin.H{
            "title": "Select the input file","error" : "Please select the input file.",
        })      
    } else {
        defer file.Close()
    }
    filename := strconv.FormatInt(time.Now().Unix(),10) 
    out, err := os.Create("./tmp/"+filename+".xml")
    panic(err)
    defer out.Close()
    _, err = io.Copy(out, file)
    panic(err)
    xmlFile, err := os.Open("./tmp/"+filename+".xml")
    panic(err)
    defer xmlFile.Close()

    // Other Implementation Details 
}

Even after providing the handling I am getting a panic in the go code. Please let me know what in the implementation am I missing.

Thanks.

    http: no such file
    File is nil.
    http: no such file
    *****
    2015/08/04 13:19:10 Panic recovery -> runtime error: invalid memory address or nil pointer dereference
    c:/go/src/runtime/panic.go:387 (0x414d36)
    c:/go/src/runtime/panic.go:42 (0x4142a5)
    c:/go/src/runtime/os_windows.go:42 (0x414066)
    c:/go/src/io/io.go:362 (0x45268f)
    D:/code/src/exmp/serverexmaple.go:45 (0x40168f)
            displayTable: _, err = io.Copy(out, file)
    D:/code/src/github.com/gin-gonic/gin/context.go:95 (0x49f8ea)
            (*Context).Next: c.handlers[c.index](c)
    D:/code/src/github.com/gin-gonic/gin/logger.go:56 (0x4ac490)
            func.007: c.Next()
    D:/code/src/github.com/gin-gonic/gin/context.go:95 (0x49f8ea)
            (*Context).Next: c.handlers[c.index](c)
    D:/code/src/github.com/gin-gonic/gin/recovery.go:43 (0x4acc80)
            func.009: c.Next()
    D:/code/src/github.com/gin-gonic/gin/context.go:95 (0x49f8ea)
            (*Context).Next: c.handlers[c.index](c)
    D:/code/src/github.com/gin-gonic/gin/gin.go:292 (0x4a46d5)
            (*Engine).handleHTTPRequest: context.Next()
    D:/code/src/github.com/gin-gonic/gin/gin.go:273 (0x4a4459)
            (*Engine).ServeHTTP: engine.handleHTTPRequest(c)
    c:/go/src/net/http/server.go:1703 (0x468415)
    c:/go/src/net/http/server.go:1204 (0x466408)
    c:/go/src/runtime/asm_386.s:2287 (0x438ea1)

Answer 1

I understand that I have made mistake with the panic handling. The validation is working if I add the return statement after the c.HTML. This will stop the function from executing the rest of the code. Thanks to @AlexAtNet for his advice and I will keep in mind in future.

if file == nil {
    log.Println("File is nil.")
    log.Println(err)
    log.Println("*****")
    c.HTML(http.StatusInternalServerError, "index.tmpl", gin.H{
        "title": "Select the input file","error" : "Please select the input file.",
    })   
    return 
}