func (c *OptionsCycle) GetChainForExpiration(e Datetime) (calls []Contract, puts []Contract, err error) {
	if !c.expirationExists(e) {
		return calls, puts, fmt.Errorf("expiration does not exist")
	}
	url := buildOptionsURL(OptionsURL, c.Symbol, e)
	result, err := fetchOptions(url)
	if err != nil {
		return
	}
	return newChain(result.Calls), newChain(result.Puts), nil
}
GetChainForExpiration fetches the option chain for the given expiration datetime.
package finance
import "fmt"
func NewCycle(symbol string) (oc OptionsCycle, err error) {
	oc = OptionsCycle{Symbol: symbol}
	oc.Expirations, oc.UnderlyingPrice, err = newCycle(symbol)
	return
}