Golang无法获取到js提交的表单数据，一直找不到原因

js用var form = new FormData(); 建立一个表单，代码如下： ``` var xmlhttp; if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari xmlhttp = new XMLHttpRequest(); } else {// code for IE6, IE5 xmlhttp = new ActiveXObject("Microsoft.XMLHTTP"); } var form = new FormData(); if (form) { var cvs = document.getElementById(cvslabel); base64Img = cvs.toDataURL("image/jpeg"); form.append("myfile", base64Img); } else alert("Ajax: Error 01"); xmlhttp.onreadystatechange = function () { if (xmlhttp.readyState == 4 && xmlhttp.status == 200) { if (xmlhttp.responseText != "0") { var retext = xmlhttp.responseText.split("|"); var uploadimg = document.getElementById("uploadimg"); if (uploadimg.value == "") uploadimg.value = retext[1]; else uploadimg.value = uploadimg.value + '|' + retext[1]; var localimghtml = '<span id="' + retext[0] + '"><table style=\"float:left;\"><tr><td valign=\"center\" height=\"100\"><img style="margin-left:5px;max-width:200px;max-height:100px;" src="' + retext[1] + '" /></td></tr>'; localimghtml += '<tr><td align=\"center\" height=\"30\" valign=\"bottom\"><input type=\"image\" src=\"bgeditor/images/delimg.jpg\" onclick=delimg("' + retext[0] + '","' + retext[1] + '"); style=\"width:25px;\" /></td></tr></table></span>'; $("#upload_pic_list").html($("#upload_pic_list").html() + localimghtml); if (ImgInsert > 0) { var bbsgoodedit = document.getElementById(labelname); bbsgoodedit.focus();//获得焦点 //localimghtml = '<img src="'+retext[1]+'" />'; //_insertimg(localimghtml,labelname) InsertImage(retext[1]); } } return true; } else { return false; } } xmlhttp.open("POST", postfile, false);//最后一个参数 false为同步 xmlhttp.send(form); ``` go代码如下： ``` if err := r.ParseForm(); err != nil { fmt.Fprintf(w, "0") } //data := r.FormValue("myfile") data := r.Form.Get("myfile") fmt.Fprintf(w,data) ``` 上面的代码始终无法接收到myfile的内容。myfile一直是空值。 请高手指点