title: Flutter: InternalLinkedHashMap' has no instance method 'cast' with matching arguments
body: <p>This is the JSON response, I need to retrieve data into a flutter. 
  <strong><em>Getting error in casting details.</em></strong></p>
  
  <pre><code>{code": 200,
      "message": "Success",
      "data": [
          {
  
             "fname": "LG",
              "lname": "Electronics",
              "email": "lg@gmail.com",
              "address": "Girish Cold Drinks, Chimanlal Girdharlal Road, Mithakhali, Navrangpura, Ahmedabad, Gujarat, India",
  
          }
      }
  </code></pre>
  
  <p>Here is the customer class </p>
  
  <pre><code>class Customer {
    int code;
    String message;
    List&lt;Data&gt; data;
    Customer({this.code, this.message, this.data});
    Customer.fromJson(Map&lt;String, dynamic&gt; json) {
      code = json['code'];
      message = json['message'];
      if (json['data'] != null) {
        data = new List&lt;Data&gt;();
        json['data'].forEach((v) {
          data.add(new Data.fromJson(v));
        });
      }
    }
    Map&lt;String, dynamic&gt; toJson() {
      final Map&lt;String, dynamic&gt; data = new Map&lt;String, dynamic&gt;();
      data['code'] = this.code;
      data['message'] = this.message;
      if (this.data != null) {
        data['data'] = this.data.map((v) =&gt; v.toJson()).toList();
      }
      return data;
    }
  }
  
  
  
    class Data {
        String fname;
        String lname;
        String email;
        String address;
  
      Data(
            {
              this.fname,
              this.lname,
              this.email,
              this.address,
              });
  
  
  
  
  
   Data.fromJson(Map&lt;String, dynamic&gt; json) {
          fname = json['fname'];
          lname = json['lname'];
          email = json['email'];
          address = json['address'];
        }
  
     Map&lt;String, dynamic&gt; toJson() {
      final Map&lt;String, dynamic&gt; data = new Map&lt;String, dynamic&gt;();
  
      data['fname'] = this.fname;
      data['lname'] = this.lname;
      data['email'] = this.email;
      data['address'] = this.address;
  
      return data;
    }
  }
  </code></pre>
  
  <p><strong>Here I am facing casting error</strong></p>
  
  <pre><code>final jsonResponse = json.decode(response.body).cast&lt;Map&lt;String, dynamic&gt;&gt;();
        List&lt;Customer&gt; listOfUsers = jsonResponse.map&lt;Customer&gt;((json) async {
          return  Customer.fromJson(json);
        }).toList()
  </code></pre>
  
  <p><strong><em>Error :Flutter: InternalLinkedHashMap' has no instance method 'cast' with matching arguments</em></strong></p>