title: Flutter http MultipartRequest field can not be Chinese Charaters?
body: <p>I try to post a form to server and here is the code:</p>
  
  <pre><code>ar request = new http.MultipartRequest("POST", _uri);
  request.fields['user_acc'] = _userAcc;
  // this issue should be solve
  request.fields['user_nick_name'] = '中文名字';
  request.fields['user_password'] = _password;
  </code></pre>
  
  <p>But the server side in the user_nick_name field always got null, note that is <strong>always</strong>, but I change it into English the server can receive that. I test on postman, the server can got Chinese correctly, so it's MultipartRequest issue on this problem.</p>
  
  <p>My question is: <strong>Why the Dart or Flutter team so careless on this so important basic library?</strong> They even not consider about this simply issue. I opened a issue on github but no-one response, I think the team is done. So I ask the develop communit here, how to solve this problem anyway?</p>
  
  <p><strong>[UPDATE]</strong>
  As kindly people suggested, I update my golang server now, if anyone else got this problem, you may wonna answer and suggestions too.</p>
  
  <pre><code>func HandleUserRegister(context *gin.Context) {
  
  userAcc := context.PostForm("user_acc")
  userAvatar := context.PostForm("user_avatar")
  userNickName := context.PostForm("user_nick_name")
  userPassword := context.PostForm("user_password")
  userPhone := context.PostForm("user_phone")
  userEmail := context.PostForm("user_email")
  userGender := context.PostForm("user_gender")
  userSign := context.PostForm("user_sign")
  
  userType := context.PostForm("user_type")
  userTypeInt, _ := strconv.Atoi(userType)
  
  log.Infof("userAcc: %s, userNickName: %s, userPassword: %s", userAcc, userNickName, userPassword)}
  </code></pre>
  
  <p>This is based on gin, and this function is the api solver. If anyone wanna help, please help me figure it out.</p>
  
  <p>OK! I update the question now, <strong>because it's really weird!</strong>. I did those test:</p>
  
  <ol>
  <li>Post multiform via Flutter to Django server, it receives Chinese filed correctly;</li>
  <li>Post multiform data via Postman, the golang(gin) server gots Chinese correctly;</li>
  <li>Post multiform data via Flutter to golang(gin) server gots <strong>Chinese field null</strong>;</li>
  </ol>
  
  <p>For more detail, I log the headers from my server for both postman(normal) and flutter (abnormal):</p>
  
  <p><strong>Postman</strong>:
  <code>
  request header: map[Content-Type:[multipart/form-data; boundary=--------------------------022341683711652813100488] Postman-Token:[855646d7-5bea-4b8f-b8df-81366226cd49] User-Agent:[PostmanRuntime/7.1.1] Content-Length:[422] Connection:[keep-alive] Cache-Control:[no-cache] Accept:[*/*] Accept-Encoding:[gzip, deflate]]
  </code>
  <strong>Flutter</strong>:
  <code>
  request header: map[User-Agent:[Dart/2.0 (dart:io)] Content-Type:[multipart/form-data; boundary=dart-http-boundary-.XUeYeqXpg4Yfyh8QhH1T5JB4zi_f3WxX9t7Taxhw91EFqhyki4] Accept-Encoding:[gzip] Content-Length:[574]]
  </code></p>
  
  <p>Does anyone can notice the difference and let me know how to change the it make server can receive the Chinese Characters?</p>