feat(engine): Added OptionFunc and With

[flc1125]

I would like to add an OptionFunc to facilitate Gin configuration.

Note: This adjustment supports downward compatibility.

Before:

package main

import "github.com/gin-gonic/gin"

func main() {
	r := gin.New()

	r.GET("/ping", func(c *gin.Context) {
		c.JSON(200, gin.H{
			"message": "pong",
		})
	})

	r.Run(":8002")
}

But now:

• New Engine

package main

import "github.com/gin-gonic/gin"

func main() {
	var fc = func(e *gin.Engine) {
		e.GET("/ping", func(c *gin.Context) {
			c.JSON(200, gin.H{
				"message": "pong",
			})
		})
		
		e.Use(gin.Recovery())
	}

	r := gin.New(fc)

	r.Run(":8002")
}

• With Engine:

package main

import "github.com/gin-gonic/gin"

func main() {
	r := gin.New()
	
	r.With(func(e *gin.Engine) {
		e.GET("/ping", func(c *gin.Context) {
			c.JSON(200, gin.H{
				"message": "pong",
			})
		})

		e.Use(gin.Recovery())
	})

	r.Run(":8002")
}

[flc1125]

@appleboy Does lint information, unrelated to PR, need to be processed?

[flc1125]

lint see #3584

[appleboy]

already fixed in #3583, Please rebase the PR.

[flc1125]

already fixed in #3583, Please rebase the PR.

It's already done

[flc1125]

😢

[flc1125]

@appleboy

[flc1125]

Okay, I'm tweaking related errors, this is devastating. 😂

[flc1125]

@appleboy Please try again. 3Q

[codecov]

Codecov Report

Merging #3572 (83dee28) into master (757a638) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #3572   +/-   ##
=======================================
  Coverage   98.63%   98.63%           
=======================================
  Files          42       42           
  Lines        3151     3156    +5     
=======================================
+ Hits         3108     3113    +5     
  Misses         29       29           
  Partials       14       14           

Flag	Coverage Δ
	98.63% <100.00%> (+<0.01%)	⬆️
go-1.18	98.54% <100.00%> (+<0.01%)	⬆️
go-1.19	98.63% <100.00%> (+<0.01%)	⬆️
go-1.20	98.63% <100.00%> (+<0.01%)	⬆️
macos-latest	98.63% <100.00%> (+<0.01%)	⬆️
ubuntu-latest	98.63% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
gin.go	99.20% <100.00%> (+0.01%)	⬆️

[appleboy]

@flc1125 Thanks.