anchor.diff:      /// Task of `Some HttpContext` after writing to the body of the response.
       ///
       member this.WriteXmlAsync (dataObj : obj) =
  -        this.SetContentType "application/xml"
  +        this.SetContentType "application/xml; charset=utf-8"
           let serializer = this.GetXmlSerializer()
           serializer.Serialize dataObj
           |> this.WriteBytesAsync
  
positive.code:                 | false ->
                      let env = this.GetHostingEnvironment()
                      Path.Combine(env.ContentRootPath, filePath)
              this.SetContentType "text/html"
              let! html = readFileAsStringAsync filePath
              return! this.WriteStringAsync html
          }
  
negative.code: let text (str : string) : HttpHandler =
      let bytes = Encoding.UTF8.GetBytes str
      fun (next : HttpFunc) (ctx : HttpContext) ->
          ctx.SetContentType "text/plain; charset=utf-8"
          ctx.WriteBytesAsync bytes
  
  /// **Description**
  