embed enhancement

[souloss]

• embed enhancement
• Add IRouter interface, test and documentation

[codecov]

Codecov Report

Merging #2885 (c32167d) into master (ef16867) will decrease coverage by 0.79%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2885      +/-   ##
==========================================
- Coverage   98.75%   97.95%   -0.80%     
==========================================
  Files          41       24      -17     
  Lines        3062      735    -2327     
==========================================
- Hits         3024      720    -2304     
+ Misses         26       10      -16     
+ Partials       12        5       -7     

Flag	Coverage Δ
go-1.13	?
go-1.14	97.95% <ø> (-0.64%)	⬇️
go-1.15	?
go-1.16	?
go-1.17	?
macos-latest	?
nomsgpack	?
ubuntu-latest	97.95% <ø> (-0.80%)	⬇️

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Impacted Files	Coverage Δ
logger.go
errors.go
tree.go
recovery.go
mode.go
response_writer.go
fs.go
binding/binding_nomsgpack.go
context.go
debug.go
... and 5 more

---

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[thinkgos]

@witchc hello , http.FS may be meet your needs. another feat: #2749
more refer see embedfs

// in testdata file

//go:embed static/css static/img static/views static/1.png static/index.html x.png
var Staticfs embed.FS

// in main

	// 嵌入绑定的文件
	cssFs, _ := fs.Sub(testdata.Staticfs, "static/css")
	r.StaticFS("/css", http.FS(cssFs))
	imgFs, _ := fs.Sub(testdata.Staticfs, "static/img")
	r.StaticFS("/img", http.FS(imgFs))