func Continuation(continuation string) CallOption {
	return func(r *Request) error {
		if continuation == "" {
			return nil
		}
		r.Header.Set(HeaderContinuation, continuation)
		return nil
	}
}
Continuation a string token returned for queries and read-feed operations if there are more results to be read. Clients can retrieve the next page of results by resubmitting the request with the x-ms-continuation request header set to this value.
package documentdb
import (
	"encoding/json"
	"strconv"
)
type Consistency string
const (
	Strong Consistency = "Strong"
	Bounded Consistency = "Bounded"
	Session Consistency = "Session"
	Eventual Consistency = "Eventual"
)
type CallOption func(r *Request) error
func PartitionKey(partitionKey interface{}) CallOption {
	var (
		pk  []byte
		err error
	)
	switch v := partitionKey.(type) {
	case json.Marshaler:
		pk, err = Serialization.Marshal(v)
	default:
		pk, err = Serialization.Marshal([]interface{}{v})
	}
	header := []string{string(pk)}
	return func(r *Request) error {
		if err != nil {
			return err
		}
		r.Header[HeaderPartitionKey] = header
		return nil
	}
}
func Upsert() CallOption {
	return func(r *Request) error {
		r.Header.Set(HeaderUpsert, "true")
		return nil
	}
}
func Limit(limit int) CallOption {
	header := strconv.Itoa(limit)
	return func(r *Request) error {
		r.Header.Set(HeaderMaxItemCount, header)
		return nil
	}
}