func EpochFormatter(key string) TimeFormatter {
	return TimeFormatter(func(t time.Time) Field {
		return Time(key, t)
	})
}
EpochFormatter uses the Time field (floating-point seconds since epoch) to
encode the entry time under the provided key.
package zap
import "time"
type JSONOption interface {
	apply(*jsonEncoder)
}
type MessageFormatter func(string) Field
func (mf MessageFormatter) apply(enc *jsonEncoder) {
	enc.messageF = mf
}
func MessageKey(key string) MessageFormatter {
	return MessageFormatter(func(msg string) Field {
		return String(key, msg)
	})
}
type TimeFormatter func(time.Time) Field
func (tf TimeFormatter) apply(enc *jsonEncoder) {
	enc.timeF = tf
}