title: problems when accessing C union field
body: <p>I'd like to access the field of C union in Go. below is my source code, but i got an error when compile it:</p>
  
  <pre><code>package main
  
  // #include &lt;stdio.h&gt;
  // #include &lt;stdlib.h&gt;
  // union bar {
  //        char   c;
  //        int    i;
  //        double d;
  // };
  import "C"
  
  import "fmt"
  
  func main() {
      var b *C.union_bar = new(C.union_bar)
      b.c = 4
      fmt.Println(b)
  }
  </code></pre>
  
  <p>when i build, i got errors like below:</p>
  
  <p>b.c undefined (type *[8]byte has no field or method c)</p>
  
  <p>Who could tell me the correct approach to access a union field?</p>