总会出现“panic: runtime error: invalid memory address or nil pointer dereference”错误

[kerncoola]

classID 354
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x174dd7e]

goroutine 1 [running]:
github.com/yann0917/dedao-dl/cmd/app.CourseInfo(0x162, 0x400, 0x203000, 0x400)
/Users/123/go/pkg/mod/github.com/yann0917/dedao-dl@v0.0.0-20210112030314-f8244ebe0873/cmd/app/course.go:33 +0x5e
github.com/yann0917/dedao-dl/cmd.courseInfo(0x162, 0xc000010018, 0xc0001abd78)
/Users/123/go/pkg/mod/github.com/yann0917/dedao-dl@v0.0.0-20210112030314-f8244ebe0873/cmd/course.go:118 +0x45
github.com/yann0917/dedao-dl/cmd.glob..func4(0x204c840, 0xc0001e3980, 0x0, 0x2, 0x0, 0x0)
/Users/123/go/pkg/mod/github.com/yann0917/dedao-dl@v0.0.0-20210112030314-f8244ebe0873/cmd/course.go:44 +0xba
github.com/spf13/cobra.(*Command).execute(0x204c840, 0xc0001e3960, 0x2, 0x2, 0x204c840, 0xc0001e3960)
/Users/123/go/pkg/mod/github.com/spf13/cobra@v1.1.1/command.go:850 +0x47c
github.com/spf13/cobra.(*Command).ExecuteC(0x204c060, 0x0, 0x0, 0xc00008e058)
/Users/123/go/pkg/mod/github.com/spf13/cobra@v1.1.1/command.go:958 +0x375
github.com/spf13/cobra.(*Command).Execute(...)
/Users/123/go/pkg/mod/github.com/spf13/cobra@v1.1.1/command.go:895
github.com/yann0917/dedao-dl/cmd.Execute(...)
/Users/123/go/pkg/mod/github.com/yann0917/dedao-dl@v0.0.0-20210112030314-f8244ebe0873/cmd/root.go:29
main.main()
/Users/123/go/pkg/mod/github.com/yann0917/dedao-dl@v0.0.0-20210112030314-f8244ebe0873/main.go:17 +0x2e

[yann0917]

1. 运行 dedao-dl course 查看购买过的课程， 看看 354 这个课程是不是你购买过的
2. 如果是未购买过的 ，这里可以做个优化，提示未购买。

[yann0917]

得到的分页策略改了，不能一次性请求所有的文章。

[yann0917]

问题已修复，并新增『每天听本书可下载』功能