添加带有滑行的golang眼镜蛇包装时出错

My glide.yaml import section is

import:
  - package: github.com/spf13/cobra

I have

import (
   "github.com/spf13/cobra"
)

in my code.

but I am getting the error

vendor/github.com/spf13/cobra/command.go:1092: c.lflags.SortFlags undefined (type *pflag.FlagSet has no field or method SortFlags)
vendor/github.com/spf13/cobra/command.go:1092: c.Flags().SortFlags undefined (type *pflag.FlagSet has no field or method SortFlags)
vendor/github.com/spf13/cobra/command.go:1240: c.parentsPflags.SortFlags undefined (type *pflag.FlagSet has no field or method SortFlags)

couples of issues on cobra repo says that can happen if pflag package is old version but in my case don't have that package installed separately. any idea what am I doing wrong? thanks in advance!