func (source source) MarshalLogObject(enc zapcore.ObjectEncoder) error {
	enc.AddString("file", source.File)
	enc.AddString("line", source.Line)
	enc.AddString("function", source.Function)
	return nil
}
MarshalLogObject implements zapcore.ObjectMarshaller interface.
package zapdriver
import (
	"runtime"
	"strconv"
	"go.uber.org/zap"
	"go.uber.org/zap/zapcore"
)
const sourceKey = "logging.googleapis.com/sourceLocation"
func SourceLocation(pc uintptr, file string, line int, ok bool) zap.Field {
	return zap.Object(sourceKey, newSource(pc, file, line, ok))
}
type source struct {
	File string `json:"file"`
	Line string `json:"line"`
	Function string `json:"function"`
}