code: func Example(exp interface{}) {
  	if a, ok := attributeDefinition(); ok {
  		if pass := a.SetExample(exp); !pass {
  			dslengine.ReportError("example value %#v is incompatible with attribute of type %s",
  				exp, a.Type.Name())
  		}
  	}
  }
docs: // Example can be used in: Attribute, Header, Param, HashOf, ArrayOf
  //
  // Example sets the example of an attribute to be used for the documentation:
  //
  //	Attributes(func() {
  //		Attribute("ID", Integer, func() {
  //			Example(1)
  //		})
  //		Attribute("name", String, func() {
  //			Example("Cabernet Sauvignon")
  //		})
  //		Attribute("price", String) //If no Example() is provided, goa generates one that fits your specification
  //	})
  //
  // If you do not want an auto-generated example for an attribute, add NoExample() to it.