context_builder.go
func (cb *ContextBuilder) SetRoutingKey(rk string) *ContextBuilder {
	if cb.CallOptions == nil {
		cb.CallOptions = new(CallOptions)
	}
	cb.CallOptions.RoutingKey = rk
	return cb
}
func (cb *ContextBuilder) SetRoutingKey(rk string) *ContextBuilder {
	if cb.CallOptions == nil {
		cb.CallOptions = new(CallOptions)
	}
	cb.CallOptions.RoutingKey = rk
	return cb
}
// SetRoutingKey sets the RoutingKey call options ("rk" transport header).