Fix minor mistake in code sample in README (#253)

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Author: omarkohl

README.md

@@ -37,7 +37,7 @@ var resp struct {
 	}
 }
 client.Query(ctx, query, &resp, variables)
-fmt.Println(query.Me.Name)
+fmt.Println(resp.Me.Name)
 // Output: Luke Skywalker
 ```