context_builder.go
func (cb *ContextBuilder) AddHeader(key, value string) *ContextBuilder {
	if cb.Headers == nil {
		cb.Headers = map[string]string{key: value}
	} else {
		cb.Headers[key] = value
	}
	return cb
}
func (cb *ContextBuilder) AddHeader(key, value string) *ContextBuilder {
	if cb.Headers == nil {
		cb.Headers = map[string]string{key: value}
	} else {
		cb.Headers[key] = value
	}
	return cb
}
// AddHeader adds a single application header to the Context.