Support Option Initialization Pattern

[ghosx]

Default:

walFile, _ := wal.Open()

Custon:

walFile, err = wal.Open(
		wal.WithDirPath(dir),
		wal.WithSegmentFileExt(".SEG"),
		wal.WithSegmentSize(wal.GB),
	)

[roseduan]

The following format is more easy to understand？

func (opt Options) WithSegmentFileExt(ext string) Options {
    opt.SegmentFileExt = ext
    return opt
}

[ghosx]

The following format is more easy to understand？

func (opt Options) WithSegmentFileExt(ext string) Options {
    opt.SegmentFileExt = ext
    return opt
}

wal.Open() support Default Options，if use your way, must be explicitly passed in each time it is used

https://dev.to/fufu/functional-options-pattern-in-go-42lm